The 560 isn't enough a jump over the 460, particularly the Superclocked model by evga (I've the same card). If you are going to upgrade to a single card solution, you'd only really find value in a 570/6950-level, and that is only at 1920x1080 or higher resolutions. And given how close we are to the 7xxx series, if you wait you can get either a better deal on this gen, or score a solid single-card solution.
Sony Zeiss 55/1.8 SSM, 24-70/4 SSM
Minolta 17-35/2.8-4 D, 100-300 APO