Now, our measurements aren't exact...  we took a network power switch/battery backup, and pulled snmp power usage every 15 seconds for a 15 minute period.  Then we wrote a script that would move the core and memory settings up and down until it found a sweet spot in MH/j for a specific card.  We ran this test on 8 different cards from 2 different vendors in the 5770 line, the results are similar for all the cards in that test.  We ran the same test on a smaller batch of 5850's and 6950's again with similar results.