I'm currently using a pair of nVidia 512Mb cards (Geforce 9800GT) in "SLI" mode, which supposedly runs them in parallel for better gaming performance. I no longer use my computer for games, basically using it for picture editing in Phosotshop CS5. The machine is a quad-core Windows 7-64 bit machine with 8Gb of RAM.
I need to remove one of the video cards in able to install a USB 3.0 adapter to run my external drives faster. The question I have is whether 1Gb of video RAM would make an appreciable difference in the way PS CS5 would run, and in what way? I have the choice of just using the 1 video card, or replacing it with one with greater memory, but do not want to spend for another video card unless the difference would be worth it.
I think you'll be fine with 1 video card. Lots of video ram makes a difference for animation and 3-D rendering but PS really puts very few demands on a video card. It is good to have Open-GL, though.