I don't understand why you guys are using 680s when the 770 is a less expensive, faster, newer card. It's basically a slightly OC'd 680.
I also bought a GTX 680 instead of GTX 770, but went through a different route, bought one (already flashed and tested on MP 5,1). I have had bad experiences with video cards in the past.
I was more concerned about heat and cost. I compared GTX 5xx, GTX 6xx and GTX 7xx series. GTX 680 is under 200 watts, runs cooler, and is cheaper online when compare to the GTX 7xx series cards (I mean already flashed and ready to use out of the box)
So I purchased GTX 680, but I also fully understand that heat and cost might not be of concerns to other users, that is just me