On paper, the GTX 680 has almost 200% more shader performance than the GTX 580, roughly 250% more texture performance, 90% more ROP performance and 100% more memory bandwidth. With the Radeon HD 7970 only being ~9% faster than the GTX 580, AMD appears to have priced itself into a corner this time around.
Any major computer upgrade generally requires a full software reinstall too. No so if you heed the advice in the guide to Upgrading a Motherboard without Reinstalling. PCSTATS Tips