It seems like you should be OK for the moment with your 500W. How many watts does that 460 gobble up?
If you have any peripherals, USB devices, secondary or tertiary monitors, etc; that you don't need, just disconnect 'em
Nope, only usb devices i've got are a mouse and a headset, only 1 monitor as well. I believe the 460 that ive got outputs about 177w under full load iirc from the benchmark articles etc.