dude i run my sli on a 450w power supply. i cant overclock my cards more than about 75core/110mem without artifacts, so power isnt really an issue. if i were able to overclock more, im sure my supply would do fine.
and no, i meant a 500w power source is pushing it.
and geek squad is affiliated with best buy, therefore im going to believe the geek squad tells you this to buy more shit you dont need from best buy.
now that i think about it i dont think overclocking makes you use more power.