A while back Rroff, big wayne posted up a graph from a review about power consumption of cards, i was interested in the sli gtx 275 results, 599w at full system load, unfortunately he didnt post up what cpu they were ran under, id like to test my own sli gtx 275, 4ghz i7 setup, psu is a corsair HX850w.I imagine the gtx 260's are similair in power draw to the 275's.
GTX275 generally has a higher clock rate out the box and extra SPs, etc. so its increased a bit over the GTX260.