I realize this thread is 2 years old, but this is to anyone else who comes across it:
Don't build a server. Go on eBay, Craigslist, or
www.servermonkey.com (which is probably the best for you, seeing as you want to configure your server) - server parts are very expensive, and it's extremely hard to build 1U machines as they are comprised of custom parts. Think of 1U servers like Apple computers - they're well fitted together, and all the parts are non-standard.
Personally, I've had great experience with Craigslist. You don't get to configure your machine, but you also don't have to pay for shipping. ServerMonkey allows you to configure, but you pay a little more and still have to pay for shipping. Go to ServerMonkey.
Hope this helps.
Disclaimer: I don't work for ServerMonkey, I'm just a loyal customer of theirs.