I dunno...after looking at the HIS 2600's reviews...it looks like the 8600 performs better than it in most situations...though not by a ton...but still.
HappySqurriel's link seems the best so far...
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 )