My last boat (34' cat) I ran 6.5" coax Focal speakers. They were awesome and I had tot tow the boat through some storms without the cover, no damage to the speakers, although i did have billet speaker covers with screens, but they still got wet sometimes.
My new boat is a 370SS Formula and I am installing only 3 pairs in this boat and putting about 800 watts to them. In my cat I had 4 pairs and for the cruiser, 3 pairs is more than enough for a very loud and CLEAR sound. The 4 pairs of Focal were louder and more clear than 6 pairs of MB Quart with more power.
I am running the Focal without question, as it is one of the best I have ever owned, and I have tried a ton of different stuff (MB Quart, Rockford, JL, Diamond).
Focal is as good as it gets. You could argue there are some at their level, but most stuff isn't even close. I run Focal Utopia's in my boat, at 1k per pair and worth every penny of it.