I'm pretty sure photoshop works with opencl so thats amd and nvidia cards. But in addition to that photoshop works fine on CPU for me haha. For programs like after effects and premiere pro though, the graphics acceleration is A LIFE SAVER. I have a gtx 660 ti and it flies in premiere. But I really don't know about other cards. It could be totally overkill, or maybe a gtx 680 would be like 500% better, I really don't know. However you can look around on other sites like this: ppbm5 has tons of premiere pro benchmarks and shows comparisons of different CUDA cards.
http://www.studio1productions.com/Articles/AfterEffects.htm
http://www.studio1productions.com/Articles/PremiereCS5.htm
How much is your budget? If you got a good card like a gtx 660 it could be used in programs like cinema 4d and blender, or 3d max, as well as gaming. Is this just for photoshop? Or what other uses?