Since it is the dynamic peaks which are causing the problem, the power requirements of the M60's are probably exceeding much greater than 80 watts of power in those instances as well. The safer purchase would be to get external amplification for the front 3.IMO you might be still at risk of damaging your speakers or receiver just going with external amplification with the centre if you continue with those same volume levels.

The Outlaw amp is some really nice gear.

I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.

-Max Payne