Don't really care. I want a good price

erf ratio. Something that won't use 450W on idle and 650W on load

Also one that runs cool. I hate gaming in 70s-80s. 6850?
I can't speak for anyone else, but my Sapphire 6850 w/ default clock/fan profile is ~38C idle, ~65C load with my case fans set on Low. (This is consistent with review sites like Hexus:
http://www.hexus.net/content/item.php?item=27053&page=15)
Systemwide idle/load power draw is on par with HD5770 (same at idle, and 7 watts more at load).
I haven't seen card-only power draws for the Sapphire, but it is probably similar to the ASUS version, which has idle wattage of 15 watts and load wattage of 88 watts (average during 3DMark loops) and 104 watts (maximum during 3DMark loops).
www.techpowerup.com/reviews/ASUS/Radeon_HD_6850_Direct_Cu/26.html
The card requires just one six-pin PCIe connector, which gives you an idea of how power-efficient it is.
With a mildly aggressive fan profile and at stock volts, it can hit 951/1236 core/memory speed which is ~22.7% overclock and produce zero errors in 90 minutes of OCCT.
Good luck with your decision, whatever you decide to get!