Every M car I owned I had Eisenmann or Akrapovic. There are many others that are good too like IPE/Remus etc.
It's personal preference but the best is to hear it in person for individual test....and I know this is almost impossible unless you know some members that are leaving close to you.
I would to car back 1st and work the way to front. Ones you remove resonators it will start to drone a bit. Just a heads up
