Never pay any attention to peak watts. It means essentially nothing except for lesser audio manufacturers to try and make it sound like their equipment is rated high, which is usually just the opposite when looking at the only rating that matters-RMS. Always buy an amp that is rated equal to or less than what the sub is rated at in RMS wattage. Otherwise you risk damaging the sub. Always look at the RMS ratings and pay no mind to peak. In your example-"1200w rms amp on a sub that is rated at 750rms 1500peak" this is the opposite of what you want. You can underpower a sub and it is fine but never overpower one or you risk damage.