http://linpc.us/
http://linpc.us/box-systems
Thanks, but all of that stuff is too slow and/or a little under powered.
You can work with Eric to choose the components you want, and he'll build a unit to suit.
You can also make a list and check for the particular components you want on Newegg, to see their current prices. Before making any purchase, check the same items on Amazon. Newegg usually has pretty good prices, but sometimes Amazon has better, on some of the selected items.
If you signup at Newegg to receive emails about special price events, you'll get pretty much daily emails, and at least two per week with Promo Codes that give extra discounts beyond the current listed price. I got my last two Seagate 2 TB hard drives for $89.99 each, my new case for $10.00 less then the already discounted price, 16 GB G.Skill low latency DDR3 1600 gamers RAM for $59.98, and a Microsoft Natural Ergonomic Keyboard 4000, which is usually $49.99, for $19.99 using the promo codes. Even then, I check Amazon before placing an order, because if Amazon gets wind of a super special at Newegg, they will either meet it, or beat it, but only for as long as the Newegg deal is in effect.