My Stero was installed in the lower helm, with a control installed on the upper helm. Meaning, I could turn it on, off, volumn, radioo, CD all from the upper.
I installed two speakers on the front deck, two in the cabin, Two on the sun deck, and two o the upper helm.
In the cabin I had 4 switches, that way I could insolate the music.
Mainly I would have the cabin off, and the upper, and the sun deck jamming while crusing.
That way, people inside could still hear themselvies talk.
My VHF radio had a ram mic in the upper helm, with the radio at the lower.
That way, when I was in the upper heading down the ICW, I could pick up that Ram Mic, and state:
Wife Bring me Another 6 pack ~~~ NOW!!!
While she was doing dishes and cooking food, you know, the woman's job.