Reccomendations for new PC

Well this is my PC
P4 2.8 GHZ
1.5 gigs ram
6600gt
and iam wondering should i buy a new videocard?

Or buy a new pc and go with this setup

Intel Core 2 Duo Processor E6600 (2x 2.4GHz/4MB L2 Cache/1066FSB)
1 gig ram
7900gtx
that would be a new comp but i wanna wait till vista comes out and direct x10 cards

The thing I really want to know is does this game take a toll on your videocard or your proccesser speed?

And if your running the game at max or high whats ur setup?