Here is a picture of the (mostly) completed wall.
The speaker sits back further than it is in the picture.
The hole in the TV cavity is the conduit that runs (eventually) to the media equipment closet in the basement. By eventually, I mean that it runs into the mechanical room below where there is another several conduits that run to the media closet itself. The whole house is " wired" (plumbed actually) this way.
The open low voltage boxes on each side are for free standing speakers should we decide we want them. The wires in them also have a path too the media closet.
There is no problem with high temperatures in the TV cavity. I also installed a 6" found duct in the floor of the fireplace cavity to which a fan can be connected to ventilate the cavity should it get warm. It would dump the warm/hot air into the cold air return for the foor. If we did that, the cool air draw for the into the cavity would be behind the TV, thus drawing cool(er) room air around it.
The cavity is designed to house a Samsung LN60F8000 or an LN65F8000. The room is too bright for a plasma, even Samsung's bright F8500. The cavity was sized to house the rear part of the TV that protrudes outward. The TV frame itself will sit over the rock, hiding the rock edges and the entire cavity itself.
The stone is real stone. It took an experienced, but not expert, installer about 2 full days to install. The tiles are 1"x2". They are mated with a mesh, but its still tedious, time consuming work. It looks much better in real life than in the picture.
You can't see it in the picture, but there are ceiling lights on either side of the TV with narrow beam (40 degree) reflector bulbs in them that shine down onto the rock at night. It looks awesome. Putting a speaker in the wall on either side of the TV would have ruined that effect.
I realize this is a very plain wall. Ie flat. My wife, I and a professional designer played with many different designs and actually prototype framed 2 different fireplaces into the space before arriving at this. This is what fit best with the space its in and the rest of the house. My inclination was for a much heavier (darker/bigger) stone on a more substantial fireplace structure. I quickly learned that wouldn't have fit in with the quasi contemporary feel for the rest of the house. However, I still have the basement to play with, so maybe something like that will end up there.
Like I said before, this is our great room, not our media room. For serious viewing we'll have a dedicated media room with projector and a full on sound system in the basement.