With my TBR exhaust (no DB killers) my g/f will sometimes stand outside and watch me pull into the garage.
The first time she did this I said to her, "Have you been waiting long for me?"
She said, "No, I heard you from inside so I just came outside to see you."
She estimated I was at the traffic signal about ~1/8 mile from my apt because she heard me downshift and slow to a stop and then speed back up.
So while I dont simply rely on my Loud pipes to save my life, they are plently loud enough to be heard by surrounding vehicles whether in front or behind. And for me any added attention I can grab aids in the aggresively defensive driving strategy I already use.
+1 on the Stebul horn, the stock one might as well be a bicycle bell.