I upgraded both the cabin and cockpit speakers.
For the cabin, the Polk Atrium 4 speakers were my choice. The stock Fusion MS-UD750 puts out 70 watts per channel at 2 ohms. That’s the same as putting out 17.5 watts at 8 ohms per channel. The Polk Audio Atrium 4 are designed to operate with 10-70 watts of power at 8 ohms. At 17.5 watts input you are a bit on the low side but still in range.
All that said, the sound out of them is great in my opinion. Not a huge amount of bass of course but an amazing improvement over the stock fusion speakers. Everyone’s ears are slightly different of course so take my recommendation with a grain of salt.
For the cockpit speakers, I went with some Kicker 45KM654 6.5” speakers. They sound great but the starboard side install was a bear! The area where these go is really, really shallow. The Kickers are too deep so you need a 1/2” spacer between the speaker and the boat fiberglass. You also need to enlarge the speaker opening a bit for the Kickers but that wasn’t difficult. If I were to do it again I’d
View attachment 25815 get a super shallow speaker.