I just purchased a MC.1 Center and a set of nice M.5's. I was asking about the difference of the M.5 later series. I think the poster is very accurate about the diffrence of the M.5 and M1 being ported. They are very, very impressive, especialy in the midrange, and for a 4 inch woofer, not bad at all. I had heard that the M1 had a tendency to be too bright, but I think the M.5 was a improvement over the M1 with more midrange, more bass and a little less highs. I am now running them in a HT set up and I love it. Someone else where said when you play movies they give you that "right there" effect, and they do. They also fill the room with sound. I could'nt be happier. I'm debating the M2 or M3 for fronts. Not if, but which one to get and then move the M.5 to the rear. BTW - michiganpat, this is all your fault for bring this up, at the AK forum. LOL !