A:Answer Yes. You can go up to 1200 watts and be fine. Essentially you buy what you need with some wiggle room. The power supply won't operate at the advertised power the whole time, think of it as it's maximum output capability. So your old 450 watt power supply can at maximum, output 450. Also having a better power supply can sometimes actually save you on power especially if you get a silver, gold or platinum rated psu. Gold usually is best bang for the buck.
