I built mine out of the Cube Cooler, the Pyle Amp, and 4 Marine Dual Speakers (2 - 6x9's and 2-6.5's). I also installed led lights, a car charger, and a spare switch on a switchboard. I also have a watertight box and a woodgrain top for all of the accessories. Sounds amazing and will last a good 15 hours off of the 275 lawn and garden battery.
The concept sounds easy to make, but make sure you have all your t's crossed and dot all the i's before powering everything through your battery... It's really easy to burn up an amp, head unit, etc if you don't know what you are doing.
PM me or email me if you want some pictures.
Good Luck