Most big amps these days use unregulated power supplies, and just like in years past, these power supplies are designed to work on a voltage range of roughly 10v -19v DC. Orions are the same thing.
Anything over 19v would kill most amps out there. Some 12v amps with regulated power supplies will blow off of anything over 16v.
Now you could just get a 16v alternator and battery setup, companies make them already.