Well, Nut, no guesstimates needed. MSi AFTERBURNER gives you whatever info you need on the in-game onscreen overlay...
A quick test in Black ops seen the RPM on the fans of the TOP card from 1700 to 2600 rpm...bottom card from 1590 to 2250 rpm...
Standard fan speed is 40%...I was playing BFBC2 at 1680 x 1050, 8X antialiasing, 8x anisotropic filtering, HBAO ON, all goodies on...I'm getting around 160 fps...max temp 65 celsius on top card...then I enabled VSYNC...temperatures dropped to 55-56..celsius...
Only drawback to those cards, is if you intend to play on triple screen and / or at high resolutions (2560 X 1600)....then, more than 1GB per card might be helpful....
Again, in BFBC2, at above settings I was getting 650mb of video ram usage...so there is a little bit of "play" still.
$230 per card is not bad, I get 20% to 40% more performance than a GTX580 (selling for $500) for $460 total...single card is always preferable I guess, in the big picture...and packs 1.5GB of RAM...
Still, that SLI experience was flawless....no stutter, no game incompatibilities... I was a little worried at first...but it was unfounded...