Drew, your results should leave you even more than just, in your words, "reasonably happy". You established that your 875 can drive your M80s to beyond safe listening levels with ease. The distortion in the speakers at 110dB with some particular program material shouldn't be a cause for concern. All speakers distort at very high sound levels(note the NRC tests on SoundStage showing significant distortion beginning at their 95dB level)and you shouldn't confuse the fact that the M80s can "handle" over a 1000 watts without being permanently damaged with the entirely different matter of playing at those levels with low distortion.
The point about permanent hearing loss that I briefly mentioned earlier in the thread may need a little more emphasis. For a table of recommended sound level limits compiled from EPA and World Health Organisation studies see the third set
here . Note that the first two sets of longer limits are for workplace situations where some long term hearing loss is considered acceptable by some. This doesn't apply at home. So, enjoy great sound with your M80s and 875, but hopefully when you're listening for enjoyment rather than running a test you'll keep those 100db+ levels just for split-second peaks.
