If I'm running 2 GTX 670s in SLI, will the i7 3770k 3.5GHz be enough to handle it?
I'm playing GW2 atm and a lot of player's have reported that it's particularly cpu dependent and thus some of them are being bottlenecked by their cpus when running SLI.
Honestly, the only feature that i7s have that i5s don't is HyperThreading, no game uses it, and no future game likely will. Certainly if they do, by the time its a necessity, your i7-3770K will be a "dinosaur" just like the C2D. (Just to avoid arguments, yes I know the C2D is still a capable CPU for daily tasks, I have one in a laptop I still use- but anything older than 4 years by my working definition is a "dinosaur")
Having said that, you may consider looking at i5-3570Ks for gaming. Now if you're getting into heavy productivity work like video editing, CAD design, etc, then you might look at the i7s, but unless you're doing that kind of stuff professionally, even then the i5-3570K has plenty of power to do the job.