Max SPL is only really limited by the power of the amp and the relationship to the room size and listening distances. I am quite certain the M2 can play as loud as most people can stand to listen to.

To add some clarity it only takes 1 Watt at 1 Meter away to achieve relatively loud levels with an anehoic spec of 87db.

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