i was not too sure that the M80s, at that price, would better my Energy 22 Ref, speakers known to be among the best 20 years ago. i thought that maybe they will be about the same, but i'm more and more inclined to think that the improvements are significant, although i would never qualify them as "night and day"; the differences are subtle, but well worth it.
I have found once you get into quality speakers the differences are never night and day and it is all about the subtleties.