What I have now, the GTX 470: http://www.newegg.com/Product/Product.aspx?Item=N82E16814125320
Possible upgrade, the GTX 560 http://www.newegg.com/Product/Product.aspx?Item=N82E16814162085
The 470 has more CUDA cores (448 vs 336) but it's also quite a bit older. I'm guessing 336 newer CUDA cores are better than 448 older ones.
The main reason I want to upgrade is to get more memory buffer. In the apps I run (C4D, PremPro, AfterFX) VRAM is more important than clock speed.
The 470 runs okay but the GPU-accelerated filters (and the particle systems in C4D) really gobble up the memory buffer. Quickly. So adding more VRAM should help. The clocks are quite a bit faster on the newer card too, though I don't know whether faster clocks will help render particles or a Lens Blur in AfterFX... can't hurt I guess.
If you have any thoughts I'd appreciate reading them. My budget is about $200. I'm sticking with NVIDIA because Adobe's GPU-accelerated filters only work on CUDA (though that appears to be changing as OpenCL processing is now part of Creative Suite 6).