One of the best thing I ever did:
Was to put in a Sony Xplod head into a homemade teak stained gimble box that is mounted underneath the overhead shelf. Then I cut out, on the port side, the 6x9 opening with the template that was provided. This set-up literally ROCKs. When fishing, you can just open the cabin door and they sound great. They have excellent bass, decent mid-range, and average highs. I have loved this set-up thoroughly while waiting for big, stinky, flat fish to bite. I know you have to cut some holes and run some wires, but I was really, really surprised at how this worked when I first heard it. I still can't quite believe it sometimes.