Only the 6950 was tested in my rig, however, the other ones were only tested on an i5-2400. Yeah, yeah, so I don't have the best equipment in the world, but I was going by other benchmarks too, like anandtech.
power consumption has nothing to do with scaling, but dual cards increase heat, and that is something the 6850 is better at. Even if it has a reference cooler, which are actually pretty rare for them, it still only has a tdp of 127 watts.
460s beat down a 480, 6850s tackle the 580.
Crossfire scales better than sli, ever since the 6000 series came out.
I've been doing some more research, and it appears you're right about the 460. 6850 @ 1000mhz is roughly equal to a 460 a 815mhz, and after 1000 the 6850 scaling goes downhill, and the 460 keeps going. This however, only refers to average framerates. I speculate that the 6870 would still maintain a healthy lead in minimum rates, as it has a 10% lead over the 560 in this regard.
The cheapest 6850 isn't even reference cooler so that's plus in its favor also.
Why are you comparing the two cards to other cards instead of each other with bench?
The 460 and 6850 are almost identical in performance at stock.
Why are you linking a review that compares scaling for the GTX 570 and HD 6950, neither of which are the cards we are talking about.
From the anandbench comparing the two cards in dual-GPU configuration directly we can see the 460 scales just as well as the 6850.
Stop grasping at straws.