Is my computer wattage "over kill"?

I have a PC set-up planned in the near future, and i am just pin-pointing how strong of a power supply i require. The newegg calculator recommends that i need around 530 watts. However, this is dis-including USB devices, cooling fans, and the like, so i am going to go a little higher than the recommendation: 550. But then this is merely a recommendation, so it is likely that some components may need the extra power sometimes, as i have read up. So i was thinking 650 W. I mean, it may be unreasonably high, but is there really any set back to having too high of a wattage?