You could ease yourself into the flatter frequency response of the M3s, by starting with the treble pulled down a little on your receiver. Every day increase it a bit, until you have the controls flat again.
_________________________
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs
-Chris