Not a free-air - still sounds great!
It's just an MTX-RT10 sub that I have a pair of from another car. I was thinking that I'd upgrade later, but it sounds just fine being pushed by a Kicker 300.1 amp (200 watts RMS). I've read all the posts about the open-air thing, but this sub really does the lob!
I did the heater install myself. I mounted the unit where the factory does, opposite the "sub enclosure", accessed throught the front drivers side seat.
I just put the boat back in storage for the week. I can take more pix on Friday if that'll work for you. Let me know if you have any other questions.