any idea what sort of peformance increase i would get by going from a 5850 to a 580? 
i game at 1680 1050 and altho i can run almost anything at max settings i would like to be able to have some more aa
a couple of games struggle a bit too like metro and the witcher 2, i know the new card isnt going to let me max them at 60fps but it should be a nice improvement to what i can play them at now
here is the system that the new card will be going in
Windows 7 64bit Home Premium
Intel Core I5-2500k
HIS iCooler V ATI Radeon HD 5850
G.Skill RipJawX 4GB (2x2GB) DDR3 1600MHz
Gigabyte P67A-UD4
Corsair HX 850W Psu
Samsung SpinPoint F3 1TB SATA
i know it would be cheaper to get another 5850 but id like stability of a single card without having to worry about profiles for games
id also like some of the physx and nvidia only effects in games like just cause 2

i game at 1680 1050 and altho i can run almost anything at max settings i would like to be able to have some more aa
a couple of games struggle a bit too like metro and the witcher 2, i know the new card isnt going to let me max them at 60fps but it should be a nice improvement to what i can play them at now
here is the system that the new card will be going in
Windows 7 64bit Home Premium
Intel Core I5-2500k
HIS iCooler V ATI Radeon HD 5850
G.Skill RipJawX 4GB (2x2GB) DDR3 1600MHz
Gigabyte P67A-UD4
Corsair HX 850W Psu
Samsung SpinPoint F3 1TB SATA
i know it would be cheaper to get another 5850 but id like stability of a single card without having to worry about profiles for games
id also like some of the physx and nvidia only effects in games like just cause 2

and thanks for the links, i was looking for that comparison site but for some reason i couldnt find it