Man, I REALLY REALLY hate to admit this...

I got an apc muffler from some guy when my muffler rusted out on my winter beater, and the car has always been a joke to me anyway, so I threw it on. Running the z6 with bone stock exhaust with the apc muffler actually sounded good... It was a little raspy at the high end of the power band. Other than that, nice and mellow. The main thing with exhaust is to have a good resonator, good cat, and a decent muffler.