Well, since someone bumped this thread into this year already...
My fiancee wants louder horns for rush hour. I have Supertones now but she's trying to decide between the Supertones and the Stebel Nautilus. The reason the Supertones might sound louder is that they're in a frequency range to which the human ear is more sensitive.
However, what I'm really here for is to ask you guys who have had the Nautiluses for a while if they still work. I'm hearing some rumors of poor reliability with them. Any truth?