Thank you, thank you, thank you! I got quite a lot of input to my questions!
I am still undecided on the MPE. From the thread I got triggered to research a downpipe (with cat) option and if I wouldn't (potentially) void the warranty, this one would be my so far favorite solution in combination with the stock exhaust (love the racy sound of it!):
http://www.akrapovic.com/#!/car/prod...96&yearId=4592
And this Sunday a fellow M2 owner from Chicagoland will let me listen to his MPE live! I will report afterwards, I am hoping that the live demonstration will let me decide on the MPE.