Your Mh will not have any "space" in the ceiling for threading wires through. ALL existing wiring is run along the edge of the ceiling.
Install the speakers along the edge of the ceiling and hide the wires behind the molding where wall meets ceiling.
On most radio systems, you can't simply add speakers to the existing system without degrading the sound or damaging the output stages of your radio. Not all speakers are the same impedance and you can't simply add/mix additional speakers anyway.
I installed an inexpensive surround sound system and installed the speakers in each corner of the front living space by running the wires as I described above. It looks and sounds great.
