Pump the brakes!
You need to know the RMS power rating of the sub you are powering.
Dont exceed the RMS power rating of the sub by more than 25%.
If you see a peak power rating on either the sub or the amp, ignor it, means nothing. Always compare RMS ratings.
Example: a Sony 12" Xplod sub, boasting 1200 watts, will only handle, 350 watts RMS, so the amp you choose to power the sub should be 350 watts RMS as well, and should not exceed more than 25% of the RMS power handling (487.5 watts).
Bottom line, know your RMS numbers, not Peak.