I have put them in closets in a room or hallway that is closest to the TV. You then use a control that is able to go through walls. My AV guy takes care of these things for me. We then run the wires through the ceiling or walls whichever is easiest. My electrician does this for me. The whole thing comes together well but the cost does add up a bit.

I would remove the fireplace insert, add crown molding to the room, find an old beam from a salvage yard, if you like a rustic look, otherwise use casings and moldings to "beef" up the face of mantle. Changing the brick is a bit of work, you will need a pry bar to safely remove the brick then you can replace it with new stone, etc. Remember to use the proper adhesive "for high temp".
The tiled area of the face of the mantle, can be a great way to add your own style, new tile mosaic, stone, river rock, sea glass, etc.
Hope this helps.