Dave,
I changed out the RCA stereo that came in ours for a Sony Surround system. I did not mount the speakers on the ceiling but it shouldn't be too hard. I ran RG6 cables for satellite uing an electical fish tape. I removed the shrouds from the vents and could fish wires from vent to vent and then to the entertainment areas in the ivingroom and bedroom. I left a pull string between the bedroom and livingroom in case I want to pull anything else later. (I learned a long time ago to always pull an extra string when you pull wires. It cuts down on labor at a later date
) All that is above the ceiling is fiberglass insulation. I tried to be careful and not move it with the fish tape.