One other point to consider as well is that you have been listening to your Polks for some 10 yrs and become accustomed to their sound, so it may take a little while to get used to your M60s or any other speaker. It would be interesting to listen to your M60s for a couple of weeks once you feel you have them set up to your liking, then give your Polks another listen to compare.

Half of communication is listening. You can't listen with your mouth.