I'll take a guess and say the reason the M22s like a little more power might be due to the ~2ohm reading in the impedance curve around 4khz at least there was that dip on the older M22Ti's and I believe on the v2s as well..

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70