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.
That's a good point and relevant to my experience. I went from Polk bookshelf speakers to M80s and still wasn't entirely wowed when I first got them. After doing more extensive listening, I started to realize just how much I'd been missing. It was an adjustment period.
