My personal experience, having too little power is what causes damage to speakers, not having too much power. I have a JBL B-380 passive 15 inch subwoofer. It was originally powered by a Sony TA-N55ES Power Amp operating in bridged mode, which produced about 300 watts. Now, the recommended amp power is 600 watts. Nevertheless, I used the TA-N55ES, thinking for movies and music it would be enough power. I was wrong. Severe clipping was common, sounding like a sledge hammer hitting a steel plate. Now, I use a Sony TA-N80ES operating in bridged mode to produce about 560 watts, which gets the job done. I have no doubt that 1000 watts to my sub or to something like a JBL L300 class product would not be too much power. I think in fact that the sound would first become unbearably loud before any damage to the speaker would occur, that's to say, I would be more concerned about damaging my ears.