As an experiment I have put a 10 amp 12V rail PSU on the rig in my sig to see if it will run. I run a hefty OC and the xl needs power also. I am only running 1 hard disk. I have had no problems at all surprisilngly. It has been stable for weeks now. It is not recommended at all that you run an underpowered PSU but if you are wondering then give it a crack.