Mo, I have my sources, but I'm not at liberty to reveal them. Okay, just kidding, of course, or maybe too many hotdogs today. Those attenuation rates are the standard ones determined by THX and others to be appropriate, and are almost universally followed. For example, Sound&Vision includes in their lab tests on receivers the crossover frequency and roll-off numbers measured, and these are nearly always at the specified rates and within a couple Hz of the selected frequency(they test 80Hz, when available). You could look up old Denon tests if you'd like.

As for the movement of the mid-driver cones, this shouldn't happen normally, but at least in Randy's case there again appear to be abnormal influences and spirits in his listening room which are trying to gain control of his M80s(and even a more powerful amplifier may not be sufficient to defeat them). Others might suggest some distortion products of the very low frequency notes, resulting in upper harmonics moving the mid cones, but I prefer the evil spirits hypothesis.

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Enjoy the music, not the equipment.