Unfortunately you are asking an nVidia related question on the Premiere Pro Hardware forum. Many of us might incidently use Photoshop and/or Lightroom but cannot answer that question for you. You probably can do better on those forums. If this was a Premiere question then I would be glad to share my experience with these boards. I own both a GTX 660 and a GTX 680.
Premiere Pro CS5 and later use the CUDA cores in nVidia cards for hardware acceleration of certain video effects
I am not aware that Photoshop or Lightroom make any use of CUDA cores... doesn't mean they don't, but as Bill says, this is in the Premiere area
You should ask in the Photoshop and/or Lightroom forums about using CUDA cores
If not, an ATI card will cost less... and then you concentrate on amount of video card ram and the ram speed and data throughput
Thanks, I didn't notice that I was on the wrong forum.