A couple of tips:  I noticed that the power supply has a switch on the side to select voltage.  I had been running with it set to 220V, and was only pulling 58 watts from the wall.  It was pretty stable like this at 850 MHz so I measured the voltage on one of the plugs and the power supply was only providing 10.8 volts.  After switching to 110V, I was reading 11.9 volts and power usage went up about 10 watts.

After doing the voltage mod, I'm running stable at 401 Kh/s and pulling 82 watts at the wall for my 10 units.