I concur. I am a 'pro-amp' guy myself when it comes to big speakers in big rooms. However, in a fairly reasonable sized room, the M22's should play 'optimally' while utilizing just the Denon. As you've said, you don't have 'golden ears'. Therefore, I highly doubt you would notice any difference at all besides the hit to your wallet in buying an amp.

My Stuff :

M80's
QS8's
VP150
EP800
Denon 4802
Emotiva XPA-3
Samsung BD-P3600
Sharp 65 Inch Aquos LCD