I have M22's in an open bookshelf with a 60" tv. I don't have boundary issues to deal with, I have them about 1/2 inch protruding from the shelf. You may get reinforced bass if you have them in an enclosure, which isn't a bad thing, I would think. There were some discussions with M22's about additional bass response when placed near a corner or a wall a while back.
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Epic Grand Master 500 - trying to fit in a VP180!