Jethro,

I'm not sure what crossover point you are using, I'll just assume 80hz. If this is the case try 100hz for the M2's and 100. You have some excellent subwoofers, let them do as much work as possible and in doing so will take some strain of the mains and allow them to play cleaner. See if this makes any difference at reference levels with the in-walls at all.

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

-Max Payne