I've been using the A-20's for about four years and couldn't be more thrilled. The A-20's have very impressive imaging and little guess work on what is coming out of them. They've been through some changes over the years as far as the company, but have always been great on the sevice. Don't know anything about the M-20's, but if they are anywhere near as good as the A's then you should check them out. Let us know the outcome.