The below picture is what I have to work with. The only difference is that I have moved the whole thing to the left and there is exactly 30" width on each side of the entertainment center. There is 20.5" of depth on the hearth and I want to get some M60's (15" depth), but I want to know how forgiving they are in regards to being so close to the rear wall. I can do some acoustical treatments if necessary. I was thinking some sort of dampening foam or panel on the brick behind the speakers or even plugging the rear port with foam? Thanks for any help.

Alternatively, I could do M22's, but I hate the thought of spending $200 on stands when that could go to speakers. \:\(