I just blew up a 450w psu running a q6600 and an 8800gt, but the cpu was overclocked, and the psu was a pos. Just make sure it's a good psu with at least 30amps across the +12v rails and 450 will be enough.
I picked up a thermaltake toughpower 650w on clearance for ~$75 and it's more than i'll ever need
OP said the q6600 won't be oced, and that's what makes the difference. The power consumption increase as q6600's 4 65nm cores are oced is massive, makes gpu power consumption look dinky. 450 watt psu with typical 12v rail ampage will do fine for stock q6600.