I have the same boat and decided to make a box for 2 12's behind the driver seat. It fills the space and provids a seat and a solid place to step while entering/exiting the boat.
The pic here doesn't show the front but it's a down firing ported box with a clear front.
Pic was taken at the Lost Isle sound off this year. You can see a 3rd 12" in the front locker, 1 more is in the back.(no I don't normally run with that much on the tower)