I've used the older MB Quart 6.5's for years and have powered them with many different amps ranging from 75w rms per channel to 150w rms per channel. I've blown a couple of tweeters and a couple of the cheap cross-overs over the years but that's about it. I think you'll find that distortion is what blows speakers rather than overpowering them. I've upgraded all the crossovers on mine and have fine-tuned the amps and have not had any problems since. Unfortunately on a boat, there are so many other noises around it's sometimes hard to hear the speakers distort before it's too late. I also set the gains on my amps to a modest level just in case someone cranks the volume all the way up, the speakers won't distort and blow (added insurance I guess you would say).