670vs680 sli

With a 3770k, i was wondering which would be better when overclocked. Also, if it was really worth the extra $100 for the 680s. Both of the cards would be msi power editions. So, that means 2 670 pe's, and 2 680 pe's. Last question: Would a corsair AX850 psu power a [email protected], and the two gpu's overclocked as well?

I really need help with this, nobody can help?

Seriously?

The 680's won't be worth the extra money. Stick with the 670's or even better, go for 7970's. 

Yes, that PSU should be perfectly fine.

I like nvidia cards more, call me biased. How much of a difference will it be if i get the 670's? I want to not have to upgrade for a few years.

Any more opinions?

IMO, don't get a 7970. I bought one and I kind of regret not getting a 670 or a 680.