A very efficent class D or H amp will be easier on your battery. I'm going with two Deka AGM 92 amp hour batteries for the stereo. You could get one very large amp hour battery like a Kinetik.
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Viking, look at my pictures of my install. I wanted the same thing for my boat.
I used MDF. The carpet I purchased on ebay. 3M spray glue to hold it down. I also kept it off the carpet on the floor board. Just in case water came in the boat.
ya i took a peice of 1/2 " plywood and cut it to fit from top strap to the floor covered it and mounded two amps to the bourd . that way you can mount what ever you want and can screw any were on the bourd