The only data we have available are from WhitePixel 5970 @ 3.7 amp, 45w
Interesting I have a differing value. I did the same thing w/ 5970 on extender cable but it wa only ~30W.
The only reason I can think of for a 50% difference is maybe WhitePixel is not downclocking the memory and thus increasing overall load and as a result the load on PCIe slot. The 5970 in question was a second gen ATI reference card (the ones made by ATI but without the "handle").
I can grab my clamp meter and check a 6950 I still have (and maybe 6970). If I get a chance I will do it this weekend.