I thought you have one 7-channel Sherwood amp.
It is pointless to attempt to measure distortion or power levels without the proper equipment.
The highs should sound very fatiguing highs when clipping. The mid and woofer drivers may also be moving in a funky, distorted way.
You might want to try measuring the C-weighted SPL, 3 feet away from one of your speakers. If you measure peaks of 115 dB with 2 channels driven from that Sherwood 7-channel amp, it's reached its 220W/channel (2-channels driven) into 4 Ohms limit. If the amp is older or has been stressed, it may not even be able to reach that limit.
The M100s should be good to about 118 dB (in room) according to the sensitivity and power handling specs.
