I haven't posted anything in this thread until then so, no, I'm not.
Dave beast just posts pro AMD - as someone else posted - drivel in all threads of this nature. My best advice OP would be to weigh up the balance of opinions that you receive while ignoring rhetoric from the likes of Dave.
I'm completely uninterested in the green vs red forums battle. I had a nVidia 6800 and 8800 as well as an ATI/AMD 9800XT, HD 4850 in crossfire and HD 6870 before now.
OP - I don't know how compatible the AMD cards are with the BenQ screens for 3D gaming (sure someone will confirm) but if you want to try gaming in 3D then the 680's are definitely compatible. This might be a moot point though as AMD cards might be OK with this screen.
As to your original question, the difference between the cards isn't all that much either way really. To me, on the balance of everything I've read, the 680 is stronger than the 7970 out the box. People moan that the 680s boost themselves while completely ignoring the point that a lot of people play with their graphics cards out the box and don't indulge in much GPU overclocking. People also complain that the 680 was
allegedly going to be a mid range part.
Depending on the overclocking performance of the particular 7970 you receive you can close the gap on the 680's and ever surpass it (like for like max overclocking comparison) at higher resolutions depending on the game. But you aren't talking lots of extra performance. Also bear in mind that reviewers generally receive golden overclocking card so you may not see the same level of performance.
As Gibbo posted, if you are interested in benchmarking as well as gaming then the 7970 looks to have more power but the 680 is overall better optimised for games and this is with the first driver release as well. Hopefully things will get even better!