Clearly building your own PC is a great choice for your wallet. I would certainly though go with some WD Raptor 10k rpm drives in raid0 (although they're pricey, 150GB for $200), and if you backup, I find raid0+1 to be unnecessary and weighty. Your call of course.
I went crossfire ATI, and in the end wish I would have gone nvidia, clearly you're making a good choice.
