I believe that the on-wall M22s are bottom ported like the on-wall M3s that I have. That helps them since they are on the wall, but I know that you are concerned about other audio "boundary" issues since the speaker plane is so close to the wall plane. Can't speak to the M22s, but I really like my M3s... I have them for surround duty right now though, so they aren't primary speakers either...
So I guess I have no actual helpful information for you, but at least you have a response to your post. LOL
