I don't know how rural it is where you live, but when I added an air horn to my truck when I lived in the city, I kept the original horn and had it wired up so that I could select which horn sounded when I hit the button. That way I could give a "polite" beep when someone was sitting through a green light, but blast someone if they were about to run into me.
Personally I like the little roadrunner "meep meep" of the stock horn--it makes people smile when they wave and this tough looking military truck beeps like a VW bug. I'll admit I have thought about a similar dual-horn setup for my HMMWV... The tactical horn really doesn't get a nitwit's attention the same way a diesel locomotive horn would.