[Alki]

My opinion is that if you are completely happy with the M3's and they are giving you what you want then why change them. I was an M1 owner for many years and now have Revel which I think is a similar sound signature. My brother has my M1's and they still function flawlessly. As a matter of fact when I go to his place for a beverage and a listen I get to thinking how much I miss the way they fill the room with great sound and would not be embarrassed to have them back.

What may also help you make up you mind is to go take a listen to some speakers that interest you and are in your price range and see if you are happier. If not then save the funds.

One last solution is that you take the funds that you would spend on the speakers and place this money aside for a future upgrade. Not touching these funds will be the hard part.