If you want better performance than both, get 480 SLI for the price of 1 x 5970
I wouldn't buy a 5970 in the first place since it's a dual gpu card; basically crossfire on 1 board.
if you plan on opverclocking and dont want to spend a ton then 460's in SLI is a good option.
If you care about the noise lvl, you really shouldnt go GTX480s. Unless you also watercool them.
GTX480 SLI is pretty nice if watercooled, but ofcourse it carries a much higher cost.
Your 850W is enough for ANY dual card setup, Except GTX480 SLI. That should tell you a few things really..
The fastest card is a Radeon HD5970 2gb, the 5970 4GB one is 25 % faster than that again, but costs alot more.
Id wait a few more weeks or a month if you need to, for the HD6950/70/90 cards
better performance with lower heat and noise than anything Nvidia has
the OC'd 4gb toxic is 20% faster at best...and the SLI 480's are only loud when at 100%, there are plenty of reviews around showing this....they dont run like that all the time so stop with the FUD mate!
http://www.tweaktown.com/reviews/3242/sapphire_radeon_hd_5970_toxic_4gb_video_card/index12.html
The Tech Report:whiste:For what it's worth, in case the graphs don't really convey this, two GTX 480s in SLI are really frickin' loud.
the OC'd 4gb toxic is 20% faster at best...and the SLI 480's are only loud when at 100%, there are plenty of reviews around showing this....they dont run like that all the time so stop with the FUD mate!
http://www.tweaktown.com/reviews/3242/sapphire_radeon_hd_5970_toxic_4gb_video_card/index12.html