the HKS actually sounds like an exhaust ;-P the tanabe medallion just sounds like a barely louder version of the stock exhaust to me.

the HKS is still quiet, it's audible under acceleration but at cruising speed you'll forget you have it. the HKS is a very deep tone and is a bit louder than the TMT.

 

Kraftwerks makes a supercharger kit and Type One Racing (T1R) offers a turbo, both are vendors here and have very helpful folks who can answer all your questions about them. I wouldn't consider FI as my Fit is my daily driver and I refuse to do anything that major to it (nevermind that you'd have to feed the thing premium gas) I live in the eco-friendly tree hugging state of West Virginia so CARB certification is not a concern for me. I am looking at the Megan Racing, T1R Response, and A-Spec headers for now as they all have enjoyed good reviews here.