If you use the JL 10w7 or 12w7 and have a heater installed behind the kick panel you will probley need a custom box and more than likley it will need to be a sealed box to keep the size small, also you will probley need to face the woofer facing out toward your feet. dig deep because you will also need a good size amp to drive it so its going to cost big $$$$$$. let me ask why? Why spend that kinda money on a W7, do you believe bigger is better? what if i told you i could use a woofer 1/3 the price of a w7, in a very basic box that would sound twice as loud with half the power, and be completly hidden. Now some people may say B.S, a big bad speaker with a ton of power be better and louder. well I am not saying it wont but you have limitations in a boat. If you are trying to put a big sub in a small space (behind the kick panel) and you are limited to alternator output if you stay stock. keep in mind a stock 23 LSV has only a 90amp output. so these are your limitations, now you could always spend more $$$$$. and fix this problem, but really how loud do you need it. I have been useing a single 10" with no modifications to the boat and its enough to vibrate the drivers seat and floor. To give you an example, The upgraded system avalible from malibu adds a kicker kx-700.5 amp and the square kicker 10" sub on the kickplate. I took a Audio Control 3050A 1/3 octive analyzer and tested the factory upgrade against my personal upgrade. Results: I was able to gain 4 decibles and have extended bass range around 25hz, a smoother bass curve from 25hz to 100hz useing one half of a 350.4 kicker amp vs the class D sub section of the 700.5 kicker amp. I also used a kicker c-10 for the sub vs solobaric s10. I personaly believe from looking at the specs that the kicker cvr-10 would be better if you would like a little more kick, but will cost a little more $$$$$.
I also prefer the kicker amp mainly because the adjustability on the face of the amp vs adjustability on the side of the JL amp. that may not seem like a big deal until you need to adjust something and the amps are mounted. also the kicker amps have fans built into them so you will not have any overheating problems. In my system i use dual 350.4 amps max amp draw is 80 amps. this is the max draw you would want if you do not want to replace the alternator. I also use dual batteries. Malibu uses a 350.4 and a 700.5 max amp draw is 130amps this could be a problem down the road. As far as the factory 6.5 kicker speakers that malibu sends with the boat they sound harsh to me due to the mylar dome tweeter they use. i would upgrade to a 6.5 speaker with a soft dome tweeter this will sound alot smoother.(brand is not really important here)go with what you like. dont waste your money on seperates in a boat, in a sealed car or a home theater yes spend the money. in a boat no. I personaly would add a preamp EQ like the kicker KQ5 or KQ9 or a audiocontrol EQS to the system if you want a little more control. Hope this helps.