My much better specification suggestions for you.
My original server still uses those specs though at this point I have re-purposed it to provide data storage to my new cloud server setup. I will add a part to this series later to discuss my new system that split the data storage from the cloud service itself. I will briefly touch on it in one of the next parts with my alternative hardware suggestions.
Here are some of my revised specs for the whole setup that I would highly recommend instead of what I went with above. The prices are based on 3/3/17 which means they maybe different depending on the time you read this and possibly sold out. I have also added Amazon links for the items I was able to find on there which means not all will have an Amazon link. I will attempt to keep this list up to date as I notice parts going out of stock. If there are some out of stock parts please contact me and bring it to my attention in case I have not noticed yet.
(Central Processing Unit)
(Random Access Memory)
(Computer Tower Case)
(Power Supply Unit)
(Operating System Hard Disk Drive)
(One Terabyte Hard Disk Drive)
(Two Terabyte Hard Disk Drive)
(Three Terabyte Hard Disk Drive)
(Four Terabyte Hard Disk Drive)
(Six Terabyte Hard Disk Drive)
(Eight Terabyte Hard Disk Drive)
(~$0.09 per Watt)
(~$0.07 per Watt)
More in depth breakdown of my reasoning for the specs I chose and more suggestions.
CPU (Central Processing Unit)
I like to start with the CPU to see the max speed I can afford for the price and go from there. The socket type and specs of the CPU will effect nearly all other parts is why I start here. I chose this CPU first AMD because AMD processors are considerably cheaper for good GHz. There are often debates that GHz is a useless compared to operations per second, but since the manufacturers don't list that I am going to go off the easiest. Generally Intel perform much better then AMD and use less power but I also tend to be unable to afford Intel so I work with what I got. You will notice my Newegg is 4GHz Dual-Core and my Amazon is 3.8GHz Dual-Core. According to the model number they are identical however Amazon has no 4GHz AMD so its possible the Amazon specs are wrong (which happens alot with CPU's on Amazon for some reason) or they really only have the 3.8GHz. Either way they are close enough that you can go with the cheapest.
I always tend to start with Asus brand of Motherboards as they are very reliable. They almost never fail unless its due to power surges or neglect such as not repairing a motherboard fan that goes out. That being said if you can find a considerably cheaper one that is a decent brand you can swap it out. A few I have used with good success over the years are ASRock (was owned by Asus originally), Gigabyte, and MSI. Ideally you want a motherboard with 4x RAM slots if you can afford it so you can add more RAM in smaller intervals, or more RAM overall. However if you get 8GB or 16GB single sticks you don't necessarily need 4 RAM Slots. The other thing you want are plenty of SATA ports which most come with 4. You can always get PCI SATA Controller cards to expand it if necessary so 4 is plenty. Make note of the max RAM and the highest RAM speeds that do not have (O.C. or Overclock) for the next step.
RAM (Random Access Memory)
Of the speeds before the O.C. or Overclock range I went with the ones that were best priced which happened to be 1600. I like the RAM that has a heat spreader even if it doesn't necessarily make a huge difference as RAM doesn't usually generate too much heat except in some cases. In the server however its possible it will receive constant use so a heat spreader is recommended. That and it provides an extra layer of potential static protection which I don't mind. I almost always buy my RAM from Newegg as their prices is consistently cheaper then Amazon with more variety. G.Skill I chose because they make good RAM at great prices. Pretty much any brand works so long as they have a lifetime warranty, are priced well, have good speeds, and have heat spreader (not always required). A few off the top of my head with good success are: Corsiar, G.Skill, Samsung, Crucial, A-Data, OC-Z, and there are many others.
Case (Computer Tower Case)
I went for the standard tower design so it would hold more hard drives and have a bit more room to work with. It is a mini tower I chose so it only has 2 hard drive slots out the gate. You can always get a bigger case or the 5.25" to 3.5" adapters to add more slots. I chose this particular case because one its really cheap, two it comes with 2 fans, and three I have used Rosewill cases in the past with good success. For normal computers and gaming ones I tend to go with Raidmax as they have some really nice cases for good prices but for this server looks didn't matter as much as I wont be looking at it often. Its hard to refuse a case that's less then $30 and not horrible to work with. It definitely is cheap and has thin metal and lots of plastic but unless your overly rough it works fine. If you have more space and budget I would recommend one with at least as many hard drive slots as your motherboard has. Ideally I would love to get one with about 6-8 external 5.25" CD Slots and get three 2x5.25" to 3x 3.5" hot swap adapters but those tend to cost quite a bit. I also don't really replace hard drives typically till they fail so though it would be great, at least for the time being, I can't justify the extra cost.
PSU (Power Supply Unit)
I often go for Raidmax because for the price they are quite good. They also have overload and overvolt protection that can help save your computer if things go bad. If you end up buying the Raidmax one I linked on Newegg I highly recommend you buy two if they still do the volume discount. It makes the cost drop clear down to about $22 plus shipping per power supply. I can always find use for another power supply eventually and its worth it to save the nearly $20 compared to buying two separate. That being said if you really only need one and cant justify a spare the EVGA I linked on Amazon would be good as well. Some brands I have used with good success are Corsair, Raidmax, EVGA, Rosewill, and quite a few others. It typically is best to get more then enough power extra so your power supply does not have to run at full capacity which prolongs the life span though not necessarily the power efficiency. I always like to go with longevity so I don't see that as problematic. I recommend using a power supply calculator to find the cheapest power supply you can that still provides extra power for the upgrades you plan on possibly making in the near future. For mine I went chose the AMD A4-7300 100% Utilization, 2x 8GB RAM DDR3, 4x SATA 7,200RPM HDDs, 3x 120mm Fans, 2x USB 3.0 devices (external hard drives possibly), and always on (24/7). Most of that is overkill such as it likely wont run 100% CPU 24/7, most my hard drives are actually 5400 RPM and I will only have 2 for a long time, etc. Based on that semi overkill suggestion I should go with 261W. If I do lower speed SATA drives and 80% CPU Usage it says 231W. So based on that I will aim for 400W to have plenty of extra without greatly increasing my cost. Now Newegg has a basic power supply calculator which always estimates much higher then whats likely to be actual usage. Which is good, but what if you want to choose for yourself how much extra you would need based closer to the actual usage? Then I recommend a fantastic one I have found and constantly use on a website called OuterVision and can be found here: http://outervision.com/power-supply-calculator
OS HDD (Operating System Hard Disk Drive)
Granted I am using the word Hard Disk Drive quite loosely here as its actually a flash drive. However the main operating system I will recommend in a later part is designed to be installed on flash drives which is great because they are very cheap compared to solid state drives or an additional hard drive. The drive used for the operating system cannot be used for anything else so don't get overkill but decent with enough extra. Overkill in my experience is anything with more then 60GB. Most times the OS never exceeds 10GB so you can even get by with a 16GB if you had to. I recommend the 32GB Samsung Fit for a few reasons, first its rather cheap at around $11. Second its highly resilient being resistant to static, water, xray, magnet, etc. Third its tiny so you can always leave it plugged in and it doesn't overhang the other USB slots making them still unusable. Fourth and possibly most importantly it does not have overheating problems, these Samsung flash drives barely get warm even after lots of constant read/write cycles.
Data Hard Drives
I did not include these in the cost total because your exact storage requirements may vary compared to mine. All you got to do is take your storage totals you can afford in your budget and times it by two if you are doing a software raid mirrored drive for data redundancy. The operating system I will go into later uses software raid and not hardware raid so you do not need to get motherboards capable of RAID. This way I figured would be the easiest to quickly compile your own system using my recommended specs as a guideline. If you want to use my exact recommendations it will make a really nice server for the cost and let you choose your exact data storage capacities.
Your grand total will vary but in my case I went with 2x 4TB so I would have to add $249.98 to my total. So using both Amazon and Newegg mixed I would end up with $215.35 part cost and $249.98 data storage cost. My total would then be $465.33 which is $15.33 over my budget but that is assuming there are no discounts, rebates, and before getting free extra money back using my method below.
Free Extra Money!
Before you make any purchases there are a few methods you can do to get free cash back extra money. If you are buying from Newegg the easiest is sign up for a free Swag Bucks account here. They will give you 1% cash back if you click on their Shop & Earn link for Newegg before you make your purchase. Unlike some of the other rebate type websites Swag Bucks actually does pay and I have made over $100 over the years though not just from their Shop & Earn. One swagbuck is equal to one penny which sounds bad but it does quickly add up. They let you choose rewards such as Amazon or lots of other stores Gift Cards. They have tons of other cash back stores as well including limited parts of Amazon. Its only parts like clothing, outdoor & sport, etc but there is that limited Amazon cash back. This is the lowest risk free money as all you need is an account to get rewarded. So if you are interested in free cash back click here to go to Swagbucks. The other methods require credit cards which give cash back but if you do not pay it back on time can cost you more then you'd earn in fees. The best method is use your credit card like a debit card and pay it off weekly so you never get charged interest. You often have a grace period of about 20 days that you won't incur interest so paying weekly works perfectly. I personally use the Amazon Visa through Chase which gives 5% Cash Back for Amazon Prime users. They also give 1% cash back everywhere else including Newegg. So if you use Newegg + Swagbucks you will get 2% on the parts bought on Newegg. If you use the Amazon Visa + Amazon Prime you will get 5% back on Amazon. So on my total $382.35 would be through Amazon giving me $19.12 cash back and $52.99 through Newegg giving me $1.06 cash back. Using just those methods that is a free $20.18 extra putting me back under budget with a bit to spare. This is not required but I highly recommend getting free extra money since your going to have to make this purchase anyway.