So what GPU to buy: References are not including AMD GPU's as I dont use them ever. You ask why well I'll tell you, the architecture is lacking to say the least.
This is how I look at it. first off sli or single? there really is know way to get high performance and some future proofing with out going SLI, unless you go with [Example] GTX 690 or titan, or something in the 1k range.
you will hear well I prefer the single card way. well you must be spending 1k or more, or you just don't want to be future proofed. most people that are looking for a high end GPU are gamers 85% or a film, pic editor 15%. k so you have the 660ti 230$/ 670 400$/ 680 500$/ 690 1k/ titan 1k. prices are give or take. now all these cards are great performers. but none of the first four even stand close to the 1k cards. but you realy need the performance that the 1k cards give to
easily!! play the new games in ultra settings and be some what future proofed. so if you cant afford 1k what to do.? well sli is your only option, the 680sli is to much your back to 1k. the 670sli you save 200$ and your right up on performance with the 1k cards. 660ti sli you cut more the have the price 460$ and you are still realy close to the 1k card performance. 660 can be found for 220$ if you really look. I have not based this off of just one benchmark I have studied so many I can't count. This is just one example but it shows what my studies have proven to me.
http://benchmarkreviews.com/images/reviews/video_cards/GTX660SLI/Batman-Arkham-City-Benchmark.jpg so point blank if you want not only great performance witch you can get out of any one of these cards we have talked about, but you want some future proofing for the next gen of game you have no choice spend 1k or go sli thats it. well that is how I see it at this point in time