The GTX Titan is a very expensive card and may be included if the 6gb of video memory would be a benefit .
I know it's more then 5 but these are the top video cards on the consumer side that are available today. There are some very expensive Quadro and FirePro cards from the professional side that are available.
I have the latest motherboard, latest cpu, but my graphic card is holding me back. What is the top five choices that will work with the latest photoshops software and windows 8.
Hi - If you are dealing with large file photo's your choice of CPU & total ram (which you already have) is more important than the video card. Your best bet is to set a budget for your video card and then compare the AMD & Nvidia choices in that price bracket.
Keep in mind when you look at the comparisons that they are mostly game related. You should look at the compute benchmarks as opposed to the game benchmarks.
All other things being equal, AMD generally has better 'compute' benchmarks with cards of equal price.