The HTM-200 is sealed, so you won't have to worry about obstructing the port if you're wall mounting. If you can mount the CBM-170 without compromising the port and without messing up the rear half of the room, I'd lean toward it, but if the mounting is questionable I'd go with the HTM-200. The problem is similar to the one I had about three years ago: my side walls have no place to let me mount my Paradigm Studio/ADP surrounds, and even the Studio/20 bookshelf speaker would be too large to accommodate. As a result, I ended up with an Axiom M3ti - realistically not as good a speaker as the Paradigms, but sharing a similar design approach and small enough to fit on my side walls. The M3ti is also rear ported, and I ended up using Axiom's "Full Metal Bracket" to get them to stand off enough from the wall to be able to breath. Here\'s a picture of the left side surround.