I am thinking of ordereing a pair of M3's. I currently have a pair of Polk Monitor 40's. Will I see a dramatic difference between these two speakers?

Jerry, as with so many of the "vs" questions, you're not likely to get a meaningful response from someone who carefully compared the two speakers at the same time under identical conditions(and which may not be similar to your conditions). The suggestion would be to try the M3s on the 30 day trial.

What is it that you dislike about the Polks that is pushing you to look at other speakers?

Jerry, every room is different as to how a speaker will sound. Besides a trial in your home with return options, you could check the Hearing Things section to see if someone is in your area for an audition, however, it would not be in your home...Can't help you on the Polks, but for teh Polks I've heard in the past, I like Axiom a lot more...