Realistically, the best choice if you are happy to spend out a bit more, would be to sell the 680 and get 2x 7950s as has been suggested, sale of the 680 would fund the majority of the cost to swap anyway, and you'd get significantly more performance.
He's wanting it for 3D though, CrossFire in Tridef can throw up a few negative scaling titles-Kingdoms of Amular-Alan Wake, there way well be a few more that I don't play, on the other hand it works on the whole in 3D though, but just letting melmac know.

It's funny isn't it? Most people who talk smack about AMD do so whilst openly admitting that they haven't got an AMD card in their computer, and some even say they've never used one, apparently, due to "all the problems" that they apparently have.
+1,
there is one thing for example yourself and I disagreeing on PhysX and after a few words threw gritted teeth, I can respect your opinion now, as it's your opinion, opinions differ from said posters posting as fact.
Your explanation sums up this/every other forum etc, anti AMD stance coming from the vast majority of the types of said posting.
There was a user here posting a reply in a recommendation thread which went along the lines of:
'AMD drivers are pathetic, they fail on this, that, utter terrible.
I'm in the same boat as the op I'm thinking about upgrading my 8800GTX'
So when did that user actually use an AMD gpu?
I'm now getting told(in the other thread I'm wrong that the 680 was faster(even overclocked) up to 12.11's even though evidence is there from April/May from a Galaxy(Nvidia) sponsored site that they were even because they only rely on 'user data' which, when I provide user data to back up what I say is then ignored by said user.