Just a thought. Most of the power (11A or more) will go to power the bed heater. From what I can tell the temperature of the bed heater is controlled by the bang-bang methode (ie: on/off, no PWM). SO you could use the bed heater output of your controllor board to switch a relay, which in turn switchtes the bed heater on/off. Now you could run the heater on AC using a LV transformer instead of the supply, and you'd need only a 5-6A supply at 12v to run the entire printer. That's what I intend to do, I'm building a home made bed heater from a thin aluminum plate and a bunch of 5w sand resistors. It will be powered off of an 18-0-18 volt 6A (at 36v) transformer and I'll switch it on and off in the primary using a SS relay.