Agree, too far away to hear at reasonable levels without cranking them up enough for your anchormates to 'enjoy'
To get any kind of sound quality from that distance, you'd need fairly large speakers, the average 6x9 would sound like the old 'two transistor' am radios from way back.
Better would be two 6x9 or 5x7, or even four smaller speakers in the cockpit with a small sub to fill out the sound.
I really enjoy my music, but really hate being forced to listen to what some people consider music. So try to keep it down enough that it doesn't carry much past the boat (or truck)
I do have amps and very good speakers in the truck, but that is (in my case) for clarity, not volume. The boats have decent car audio systems, with speakers that I can move out to the cockpit when I want, or leave well secured in the cabin. May not be secure when in the cockpit, but if I'm worried about something getting bounced around, odds are I will have already secured everything.