This is going to sound stupid, but what are the energy implications of "bigger" power supplies? It figures that the bigger a power supply is the more energy it will pull from the mains... But is that necessarily true? I mean, I know there are differences in the efficiency etc of supplies and it makes sense that if the components in a PC only draw X amount of power, then the PSU will only use X amount... Otherwise, what happens with the excess energy... Can anybody make sense of things for me?