RM, welcome. That procedure for having the sub level about at 0 on your Pioneer isn't unreasonable, but there's certainly nothing essential about it. As long as there would be a little room for adjustment, either up or down, things would be fine. As to bumping the sub up a few dB(from the setting at 0)I'd disagree; MCACC already has the sub properly balanced in relation to the other speakers. Some listeners don't want just balance, they really want to "hear" the sub that they paid good money for, especially on movies, so they set it a few dB "hot".
As to the crossover point, along with you and John(bridgman), I'm totally puzzled by what you report. I have M22s and when I experimented using them with a sub I used the commonly recommended 80Hz crossover with good results. The M22s have good smooth response in the 80Hz area and below and bumping the crossover up to 100Hz should have no such effect. The mystery remains.
