On my 300D The Down Pipe was broken in 2. It sounded like it had a foot of exhaust pipe (which it basically did since the 2 half of the exhaust system wasn't being used)
It was kinda loud (you had to yell if you were standing out side of the car and the engine was above Idle) but it wasn't bad. My friend said that he could hear my car from 7 houses down when he was inside the house though
But I recommend that you keep the muffler on since you don't want exhaust gases coming into the car (I didn't have the problem since I left the windows down all the time, we can do that in Texas).