In my dorm my room mate has his machine plugged into the same outlet as we have the tv, the micro wave, and both mini fridges. He has played Fallout 3 while I was watching the Daily show and nuking some Ramen. Nothing bad has ever come of it.
my friend Difolo on tech-forums is gonna use 2 GTX 280 in SLI, Core i7 920, and Z-5500 5.1 speakers. His PSU is a Corsair with 750 watts. Do you think that is enough to power his system? He still has yet to get a mobo and 6GBs of DDR3 1600 RAM.