I had a recent very disappointing experience with Dinan's exhaust. PM me if you want the details, but needless to say, I will not be buying a Dinan product ever again.
My first question for anyone looking for an exhaust is what is your tolerance for drone and noise/vibration being transfered into the car? That honest answer will put you on the right path for your exhaust. There are plenty of aggressive and good sounding exhausts. But few that are refined with no drone, etc.
Current: 2014 F10 M5
Previous: 2015 F80 M3, 2013 E92 M3, 2013 F10 M5, 2009 E90 M3, 1998 E36 M3