You can run subs that are free air. Clarion makes them and I know that they sound good in that boat. The problem with free air is that sometimes they sound good and then in another application they do not. I have used the clarions in your app however and they work well. Easy install with them.
Now if you want to get picky then your tweeter should be farther away from you then the mid base that it runs with. This can be hard to do but some planning and moving things around you can ussually pull it off.

Jon

Thanks for the tips.

If anyone has any pics of how they mounted speakers in their dash, or any custom work I'd love to see them. Looking for ideas.

Thank you