Jinglehorse.net Custom Computers
A good website for buying your own customized computer is Jinglehorse (www.jinglehorse.net). One of the members of my old gaming guild, The Cabal, is a partner of this company. They build custom computers that you can configure online, they sell every type of computer component you could need for your system, and their site provides some very helpful computer buying guides. I think they offer solid systems at a good price.