Depends how important music is to you when boating ........
When I'm in the car - my music is played 90% of the time - 10% Radio
When I'm boating - I hardly ever use the stereo ..... it might be 2%
That's the first thing you need to decide -
If I was building a boat - yeh I would have a hard wired head unit with decent speakers ....... when underway you really need to crank up the volume & none of those portable speakers cut the mustard.
Chris