I build my own as well.  It's my opinion that to do anything else is literally tossing $$ out a window.  If you can put together a 7 part lego car you can build a pc.  Just last week I assisted my Uncle in building his first (we talked on phone as he did it) for a total of 850$ we built him a system that we than compared with a similarly specc'd dell , That dell cost 1400.

I am:  aka Velocity3d