Hi, sorry, I am confused as to the layout described. Regarding side wall proximity with the MPX, not a problem for surround application. Yes, the dynamat boxes provide significantly more sound blocking than the insulation alone, if that's a problem.

Sorry, I know it was confusing. I've attached a picture to try and explain better. Basically I have a single 17x13" area that I can install rear speakers in the ceiling. If I choose the HTR 7000s they will be ~7" from the side wall, and the manual says to have at least 12". I'm wondering if I should go with the MPX or HTR 7000s for the rears.

Gotcha. I'd suggest the HTR, pointed toward your center listening position.