I have heard almost all of them. I went with the Cargraphic Export Loud exhaust in the end. It's more expensive, but the quality is unmatched. The Fabspeed Super Sport is insanely loud but the welds begin to crack after 3-4,000 miles.
The EVO intake is nice but watch your MAF sensor. It will go out more ofter with the intake.
Head over to this site for all the info you want on any Porsche uograde. The have site sponsors that are excellent to deal with.
www.6speedonline.com