They have been used in audio systems with success. Advanced consumer world champion in SQ for USACI used a smaller one under the hood for his 6 channel Tru Technologies amp. In this case I would put the one I recommended in the back.
Just so the world knows, the Kinetik Racing and Kinetik Audio batteries are identical, except for the color. I called them about this and they said it was true. I thought that the red ones would be diffferent, but they are not. Buy whichever you get a better deal on.
You can convert your charging system from the standard 12v to a 16v system. It requires extensive knowledge of electronics. It is not a simple task for the average guy. You have two choices for running your standard 12v electronics. You can use Kinetik HC16V batteries which have both 12v and 16v posts. Or you can us a step down box that will convert a 16v charge (18.8v~19.2v) down 2.4v/3.6v.