I think getting 8 gigs of ram (vs. 6) would be more of a benefit. I notice I am swapping quite a bit even with 8 gigs of ram and 4 wow instances with Vista 64.

Maybe even get 2x of the 6 gig kits. That would be REALLY nice. I think that would be better than another HD.

But getting 2x hard drives would be nice, 10K RPM drives would be better.