I use M3 for surround at the moment with M22 for mains, a few months ago Got a Vp160 Absolutely love it.
The only big difference i've noticed is in power supply.
I went from a budget amp. Onkyo 525.
Wanted to get away from Onkyo and purchased a Tascam PA-R200.
Witch turns out to be a rebadged Onkyo Integra 30.4 But it's fantastic so much more headroom Toroidal transformers makes a tone of difference in sound quality.