This is like one of those: "What's the best _____ ?" questions.
Why not just go shopping? Best Buy would be a good start, then the internet.
I have a cassette deck, a cassette adapter for my iPod, and a 10 disc CD changer. From your post we have no idea what kinda music platform you're running.
My wife says to me, "The only thing you don't have for your music on the boat is your phonograph player."
"That's next," I replied. Along with our old jenga game.
You'll find soon enough that anything that can fly around the cabin of your boat simply isn't worth NOT getting a "head end" fixed unit.
Why not keep it silent when running, and just use your headphones? Your neighbors might appreciate it at midnight.
