To test power consumption today we are using a Keithley Integra unit and we measure power consumption from the VGA card inputs, not the system wide drain. We measure results while gaming in Crysis Warhead and record the results.
The HD6850 is a very efficient card, and the Powercolor Single Slot Edition maintains a 100-103 watt drain when gaming. Ideal power figures to ensure a CrossfireX configuration doesn't rack up huge electricity bills.