Don't get an 8600...they're relatively old...stick with something as good as an 8800 or above. Crysis would probably run around medium-high on an 8600 with decent framerates...no AA or anything though.
You can get 8800s for good prices now...I would actually recommend a Radeon 4850...they're a little better and you can find them for $150.
LEFT4DEAD411.COM
Bet with disolitude: Left4Dead will have a higher Metacritic rating than Project Origin, 3 months after the second game's release. (hasn't been 3 months but it looks like I won :-p )