Go with a hybrid system ... I have the stock horns on my Aurora as well as a kill at 100 paces air horns. The stock horns fire right up when you hit the button, but the air horns take a second for the compressor to charge up. A slight touch of the horn for that anemic factory sound, and just hold it longer for a 130db of sonic assault. Worth noting, that's a separate compressor system, and you might not get the same delay on smaller horns.
PS ... recently added air horns to my motorcycle. The Stebel #11690019 is a compact one piece unit that would probably mount right up to the stock bracket on the TCs and shouldn't stress the stock relay and wiring.