Yea, I mean I've done research on the cards and was debating between the 670 and the 680 still not sure which I want to go with lol. The texel rate seems to be the big difference between the 670 and the 680, other than that they seem to be a decent match.
From everything Ive seen, The 670 performs just a FEW frames lower than the 680. But is also $100 cheaper.
-5 ish FPS or + $100? lol
Guess it depends on personal pref at the end.
Texel Fill rates is for anisotropic filtering i believe
I would say, 680 for 2560x1400 and 670 for 1920X1080