The best way to do it is build it yourself. Its a great learning experience and there are many people that can help you, including myself. Not only will you have a great system, but you'll have the satisfaction of an accomplishment. And as ER pointed out, mwave.com is a good place to get parts. You could save some serious $$ by doing it yourself too.
Personally, though, I've seen a lot of systemax lemons out there, sold through HSN. I built one for someone because of a bad computer - they got everything they ordered form HSN on the systemax, and I built it for $700 less than they paid. They were happy.