6800GS , performs almost on par with the 6800GT, in some games it performs a little better while others it performs a little worse.... that in my book = equal performanc... except the 6800GS is only $200. clubit.com has it for 200.
HD perfromance only increases Loading, or Install speeds. I just get EIDE cause i dont care how fast stuff loads. but if you do go SATA.
If your capturing and encoding Video, Definatly get 2 seperate HDDs not 1 Big one.... when you encode a Video from 1 format to another, you wont 2 harddrives because it has to read/write at the same time.. having 2 drives will double that speed and limit fragmentation.
i may be wrong, but wont that system pritty much run any game at High to Max settings?
i tested this comp in the past... 2.4p4, 2gRam, 6800nu agp.. that ran HL2 at Very high, Farcry at Very High, Doom3 at Ultra, BF2 at High/Medium.