I had the intention of doing like a mega update in the near future so I can play all the DX10 games when they come out, I just don't have any money :D
I dont think you should go for a 8800, they are very exspensive now. I think the 7950GT is a good chocie.
I think the main problem is that you're in Australia. The only good servers to play on are thousands of miles away from you and that's not exactly asking for a good ping.
What kind of ping do you usually get when you play?