I currently am not rocking it but have decided on going this route. The gains are on the website for AAM and they seem to be the best gains for any kind of "cat back exhaust." As far as loudness they seem pretty loud, haha.
I found this the other day and that's actually what made me decide on it pretty loud and sounds pretty awesome. Also great dyno gains.
Nismo 370Z with AAM Exhaust - YouTube
Heres the site with the dyno gains too.
AAM Competition - Nissan GT-R, 370Z Turbo Performance Specialists