Problem with all the amps you guys are talking about abouve is they measure them one channel at a a time, where as a lot of power amps measure the ouput with all channels driven.
I know for a fact my old Parasound rated at 85w was a lot more controlled and louder than my Denon A1 intergrated rated at 140w. However the Denon sounded louder, what I mean is when they were both calibrated to output 75db at -0db the denon sounded a lot louder, but this is distortion not real volume. Add a 200 or 300w power amp to your system and play it at reference and it will seem even quieter, it won't be, but there is just more control there because of the extra headroom.
David I would say that if you have a speaker requiring 300 watts and you drive it with a 150watt amp you are far more likely to damage that speaker than if the figures were the other way round.