LOL what new games would do 120hz not a lot only older games.
Judging by your spec, you should be in a good enough position to tell us what recent games do run 120FPS.
If you're obvious to it, then it's a lot of games. Bioshock on the latest cards runs at ridiculous framerates and it's not that old a game. Last reviews I saw, the GTX295 was getting around 300FPS average at max settings 1920x1200.
There will be a load of games that'll run at 120FPS.
My 4850s can get around that rate in some new games and they're not particularly powerful compared to the latest stuff.