[LWJ]

So I did a bunch of this 10-15 years ago.

My theater looks like yours. I am fine with it.

But, I have several places with wall / ceiling speakers in my home. Here is what I learned: wall speakers - make a box with 2x4's and caulk them to make a air tight "speaker box" in which to place your speakers. Load the box with a little loose fiberglass insulation. This is supposed to be highly beneficial and I will report that I am very pleased with my middle of the road speakers in such enclosures. The subwoofer in a wall (at the time - not sure now) was expensive and controversial. I don't have one. You can usually hide a sub most anywhere in a room as the waves are omnidirectional.

Also, Denon receivers have a microphone and protocol that is used to calibrate the room to the speakers. I believe that this is pretty beneficial so that you could use down facing front speakers or similar.