Which GPU will perform better in todays games (BF3,Crysis 2,Metro 2033)
They are both about the same to be honest, its all about how much you are willing to pay, if you can afford the 680, get it. It cant produce as many FPS as the 7970, but nvdia cards have less frame latency (smoother gameplay) and also support physX.
I think your biggest concern is the Direct CU II's slot massiveness inside your case. Overtime it'll slowly become slanted due to the heaviness, potential damage. Ever since I've seen that card, I'm thinking...that has the break something
Buy a support beam for those fat beasts