Your problem is you made the Rookie mistake of putting a screen above a fireplace. This should never be done. The screen s too high, and the screen gets too much heat, so it will give trouble. Next it makes using a center next to impossible. So the TV over the fireplace is what you need to change and fix your walls.
I know it is nice to enjoy TV, by the fire, but this is how you do it.
That is a 3.1 system with everything in wall including the sub.