Forget about the HD 7970, it will result is far less performance than a CUDA enabled nVidia card. Think about a factor 12 for PR.
OpenGL is supported by all cards, so the main difference is in hardware supported MPE or 3D-RayTracing in AE.
For a GTX 670/680 you must be planning quite a system, at least an i7-3930K overclocked, 32+ GB, and a very nice disk setup.
Buying a system often precludes overclocking (Dell, HP, and the like) and then a 670/680 is complete overkill, at least from a PR perspective. So, tell us what kind of system you are planning to buy and budget range.
Yes, sorry, I forgot to mention the other components.
It will be a 3930k, 32gb ram, 240gb ssd...
So you suggest to forget about ATI?
And... is there anything about the future cs7 and this cuda/opencl fight?
If that's all, a GTX 660 is more than enough.
For Photoshop it really doesn't matter ATI/NVIDIA since both work with OpenGL and OpenCL and for PR and AE NVIDIA better, am I right?
Anyway, i keep reading people saying that OpenCL is the future (and here ATI leads).
I'm going mad... :D
OpenCL may be better or not in the future, time will tell, but the future is not here and currently nVidia is your only sensible choice.