ill have 2 monitors at 1920x1080 and one at 1280x720
i guess my next question would be which is the best 7970?
Wait so you plan to use surround/crossfire with those 3 monitors? or do you only game on one? If you plan on using those 3 your resolution would only be 3840x720 and at that resolution I would go with the 670. If you get another 1080p monitor the memory bandwidth/vram MIGHT be an issue and then i would go with a 7970.
(from my experience nvidia cards are slightly "smoother" than the amds but that might just be me.)