Do you have a reason to move away from a single 480?
As far as i gather a 480 will run all games maxed out.
While the 480s are awesome cards, they still won't give you fps to match a standard monitor's 60Hz refresh rates.
The 680s will keep you at or above that 60Hz mark with full details/ultra mode and full AA at most resolutions with just about everything. The 480s will not.
The 680s run cooler, use less power and exceed the performance of the a 480 considerably:http://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_680/9.html
The review at the link above displays a comparison between the 480s, 580s, and 680s as well as the radeon cards.
If OP can do it, I'd recommend the upgrade of the video card (if you can get your hands on one).