I think the "big three" in Sirens are:
Federal (the mighty "Q")
Sterling (ie, the Model 20)
B&M (the "Coaster", I think?)
A buddy of mine has a St. Louis-made siren on his '41 Diamond-T. Can't remember the brand, but it's VERY throaty, with a real gurgly growl. Pretty neat.
I've admired my Sterling 6-volt Model 20 ever since I discovered that it draws a miserly 20 amps (hence the name). I kinda like the long wind-up time, also. Federal-Qs, as well as my buddy's, can draw a
whopping 100 amps!!! 
-Michael
