JBroll
I MIX WITH PHYSICS!!!!
If that's what you're after, I put together a dual-core, 64-bit box with 2 gigs of ram and a fancy-assed ATI x1900 for a bit under $600 over the summer, and that was before quad-core exploded as much as it has... build one yourself or find someone who knows what they're doing to take care of that, don't fucking bother with retail computers or companies like Dell because they just rip you the fuck off on things you don't need or want while overcharging for the components you want.
Jeff
Jeff