Graphics Cards

I am going to be building a new rig and i was contemplating dual EVGA ACX superclocked 770 graphics cards, or a single 780.
What would be better bang for buck. dual 770`s are about 850$ while a 780 is aboiut 650.

Thanks for feed back

Dual 770s will offer noticeably more performance, but the 780 will use less power, eliminate the issues of SLI, and offer room for expansion with up to 3 more 780s. I'd get the 780, and save money, if you don't get 7950 CF.

Thanks for that :P