I have the Gen 3 stillen with Berk test pipes and Stillen cat back. Loud but performance is better than what I could have imagined. Check engine light is on with test pipes. I've heard there is a work around for that. Heres the link to you-tube if you want to see what it sounds like
Nissan 370z with Stillen Cat Back Exhaust, Berk Test Pipes, and Stillen Gen 3 Intakes - YouTube