I can echo no 1 dave's findings, made the move from gtx 470's to a single windforce gtx 670. A great reduction in temps, 65c max on the 670 on auto fan which is extremely quiet, (card is clocked at +130 core, +770 memory), boosting to 1320mhz, and 7586mhz). The 470's at 750mhz core were hitting 75-70c with a custom fan profile, still quite loud. Total system power use with the 470's was 630w at the wall in game, around 370w in game with the 670. That was with my old i7 920 @4.0ghz, now running an i5 3570k @4.2ghz and power draw in game is 330w.
Fps wise, im getting much better minimums and averages, and able to max out bf3 at 1920x1200, ultra settings, x4msaa without having to worry about vram issues. The card will hold a steady 60 fps in bf3, (v-sync enabled). With v-sync off it can hold 70fps, in no doubt helped though by having a pretty decent overclock on it.