A 4850x2 is as fast as 5670 in Xfire mode. Nvidia's non OC GTX460 in SLI is as fast
as Two 5850 in Xfire mode sometimes faster depending on the games. For the
case of some factory heavily overclocked GTX460 like the Palit's Sonic Platinum
GTX460 is like the performance of two non OC 5870 on Xfire mode.
Thats how fast a GTX460 is.
As far as WOW Cataclysm is concerned using GTX460 in SLI, you can play @
1920 x 1200 resolution without any lags and in ultra settings, as long as your
procie is a high end dual core one no matter if its AMD or Intel, as long as its clock
speed is 2.9Ghz or higher.
Well, if two 5850 is you choice specially if you buy the factory over clocked ones like the Power Color 5850PCS+ or the Sapphire 5850 Toxic edition ones, then all you can do is sit back, relax and enjoy playing WOW cataclysm or other very high end demanding games without any lags or glitches. Even if you buy two non OC 5850s and manually overclocked it, still you'll enjoy many latest demanding other than WOW cataclysm at very high resolutions.
The difference in performance of a 4850x2 against. two 5850 in Xfire mode is i think around 30-50 percent depending on the games (not sure though, but its close on those ranges) because there's also a factor of FPS increase when using quad core or 6 core processors as compared to high end dual core ones.
I allready have the 4850 x2...I never thougt it would lag in wow, but sometimes it does and not only in Dalaran.
Today I was flying around in Dragonblight and got 10 fps. It's not like I have a ton of things running in the background or somethihg like that. I reinstalled this computer a week ago and switched from windows xp to windows 7.
Maybe someone can point me to the video settings that matter the most ? I read a few times shadows and draw distance are important. To be honest I don't want to lower draw distance...It's just to important for me. I'll give shadows a try, but really this computer should be able to play wow without turning down video settings too much,