As mentioned earlier in this thread it is apparent that your Denon amp section is running out of juice before you are achieving the volume levels you desire; creating amp clipping. If you are experiencing an actual speaker part blowing, then you are nowhere near the power level you need. When your amplifier starts to run out of power it begins by revealing itself as a slight harshness. As you go up in volume from that point the harshness will get worse and eventually you will take out a component, generally the tweeter. The dynamic content of music and movies is very demanding on the amplifier. Even at moderate listening levels you need a lot of power in reserve to not experience clipping, or harshness, in these dynamic peaks. Your receiver has pre-amp outputs so you can easily add an external amplifier. I would suggest going all the way to the ADA1500-7 for your system. It has 650 watts per channel available for your M80s and lots of dynamic headroom ADA1500
. Loud and clean is a wonderful thing to experience. And you will not blow any components.
Again as mentioned earlier, be sure to change the setting for your M80s to small in your receiver. The crossover point is something you may want to experiment with but I would suggest starting at 80Hz for every channel.