Thanks everyone for the input. Yes, I would like the sound to go on and off with the flip of the wall switch. To try and build off of what I have already assembled, I ordered some computer speakers with an aux input. My hope is that with these positioned behind the unit at each side, pointed outward (through the small gap that exists between the wall and the fireplace), this will eliminate the echoey sound I am currently getting, as well as give me better sound quality.
The largest obstacle now is get the sound out without getting muffled or echoed too much. I don't want the speakers to be visible. So I suppose we'll see how the next experiment goes once the computer speakers arrive.
Thanks again everyone. I've been wanting to do this since we moved in over a year ago.
Yes, pointed outward, even if that is not directly at the person. It will still sound right, even if pointed to the side, as long as nothing is obstructing the speaker grills from pointing into the open space of the room.