Are you using the ray-traced renderer to create 3d geometry? If not, the issue is irrelevant as CS6 doesn't use the GPU for much beyond that. (Details on AE's use of GPU here.)
If you are using the ray-traced renderer, I'd recommend getting a GPU that works with it or getting a third-party option that can actually use your GPU like Zaxwerks 3d Invigorator or Element 3D to do your 3d stuff.
Now, to answer your actual question: That graphics card was not out when CS6 was released. NVIDIA changed their Optix library in that generation of cards. The ray-traced renderer uses the Optix library to do its thing. NVIDIA's change means that the ray-traced renderer cannot work on that card unless you find some way to update AE's Optix library to go with it. (Which I've heard rumors of people doing, but you do that sort of thing at your own risk.)
Again, the ray-traced renderer is okay, but even though I have a GPU that can make use of the ray-traced renderer, I've never used it. There are better ways to do 3d.