azeem40, I beleive you meant to say sli gtx680's can play bf3 at 50 fps. A single 680 will struggle just as a single 7970 will unless you turn the quality down to a combination of med/high. Here is the review:http://www.hardocp.com/article/2012/03/28/nvidia_kepler_geforce_gtx_680_sli_video_card_review/5
They do talk about the 2GB of VRAM on the 680 bottlenecking but the two setups are comparable with the 7970's slightly edging out the 680's. I think it is because the 680's have better sli scaling than the 7970's. Eyefinity works as if you have one large monitor and I have read(though I can't remember where) that 3dsurround still acts as though you have 3 monitors by throttling the framerates on the two peripheral monitors in order to be able to run the main display with higher framerates. Apparently, the reasoning behind this is that you focus on the main display so noone will notice if the side monitors are running with reduced framerate. For me, the peripheral frame rate issue and having only 2GB of VRAM was enough for me to stick with AMD. Also, the availability as well better cooler options. I just ordered one XFX 7970 DD and I expect to order the second this weekend when my 6990 sells. Gotta love XFX for putting a decent cooler on the card and giving you a lifetime warranty with it.