I had a pair of Emgo reverse-cones on my '03 for a while, but they were REALLY obnoxious.
Check out the Thrush universal cans (i.e., "Cherry Bombs"). They're still plenty loud but take the harshness out. They're inexpensive, durable, look cool (I think), and it's not that hard to fab up a bracket to support them.
--Jaeger
