That's a pretty sweet application, good info! I can put my media center AthlonX2 to 4.0x instead of 6.5x for cool 'n quiet, plus shave off some volts.
Here's my mining Sempron undervolted, it's probably drawing about 1 watt at 600MHz @ .0784v (considering it's max power is 40W at 2700MHz/1.3v):