When it comes to stereos there is infinite amount of possibilities. You can basically do anything to your car or truck. Just take these pictures I have here as an example you got three T.Vs in one of them and like fifteen subs on the other.

It takes a lot of power to power all of these systems but it is possible. You just got to get the right amount of batteries and the right cabling.

People usually do it just for fun and others do it for competitions and to make their car sound GOOOD.