Exactly, this is why I don't suggest multi-video card systems because a single card can take care of up to 2560x1600 on maximum detail at smooth framerates easily. And if you're getting over 60FPS, there's no point, because most monitors have a refresh rate of that and all you're going to get is screen tearing.
Unless you want to play star citizen on max settings.
But hey, that game isn't out and won't be for at least a year and a half.
My wallet will hate my when that game comes out though, because I doubt my wimpy single 760 can handle that game.