I would recommend doing either the Cargraphic E92 System, The AC Schnitzer/Remus setup or the Eisenmann.... Please feel free to contact me for pricing/availability

Also, Tubi recently released their system for the M3... although i havent heard it in person, the sound clips sounds pretty good...

 

Akrapovic?

 

^That's what I'm going with. Not cheap, but its got the best performance, and is a vital step to turning my car into a road going M3 GT4.

 

There are so many fine systems for different budgets, sound, performance. I have heard AA and Akrapovic in person and they both sounded amazing.

 

I had the Akrapovic on my car. Fit and finish are top notch. Probably the nicest system out there for the M3. Full titanium, so you get some serious weight savings. It is on the quieter side though. Perfect for a DD. Good performance gains too, but not as much as the full cat-less systems such as the Gintani. I probably could have picked up an additional 10whp with the Gintani setup.

 

^I think the Gintani would get to be a little much for a DD. I've heard a TX e90M with the setup you described and it is LOUD!!
YouTube - e90 M3 with full catless Gintani sound - Powerchip dyno tune

 

Super Sprint or Eisenmann.