Best single for 3 1080p monitors
No more than £600. I don't particularly want to sli or crossfire because im watercooling but if it is still no more than £600 and is better than a single card then I will. Thanks
As you can see here http://uk.hardware.info/reviews/4632/36/geforce-gtx-700-series-sli-review-geforce-gtx-760770780-in-sli-and-3-way-sli-how-many-cards-do-you-need
A single GPU(GTX 780) would be able to play most games on Medium bar games such as Metro/Hitman/Far Cry/Crysis. A stronger and more trouble some duel 7970 is the 7990, this would allow you to get a better FPS in games compared to the GTX780 but arise the problems of microstuttering, AMD have released a new driver but according to TOMSHARDWARE http://www.tomshardware.com/reviews/dual-graphics-crossfire-benchmark,3583.html gameplay still feels the same.
So the best single would be a GTX780 and OC it to the max potential.