One thing you seem to be overlooking is fans, Lots of fans!!! Both case and CPU. If you can afford them go for the 10,000rpm Sata drives. They are expensive. I'd up the CPU to 3 gig. RAM looks good. Consider the power supply too. 450W is a good choice. Lastly there is the buss speed of the Motherboard itself. Get the fastest that is compatable with the CPU, RAM and the hard drives. No sense getting fast components and not being able to communicate with each other fast enough. Clean all fans at least every two weeks, more often if you live, like I do, in a dusty environment.

I must remember to remember what it was I had to remember.