I've never heard of amps being designed for wakeboard boats so they could be louder
When my top is off my system is significantly louder, the speakers anyway, not so much the subs.
Are you referring to Wetsounds speakers? Those are loud, but honestly get a regular coax, I've had mine in my doors for two years now without any water issues. If I remember right those speakers aren't cheap either...My amps get minor moisture on them but nothing to kill them. Insulate around everything if you can and you'll be alright