That REALLY sounds good from the inside
With todays strict noise regulations, audio enhancement in the cabin is somewhat difficult to avoid because of need of sound proofing engine bay etc. If what we hear is the engines note, just enhanced by speakers I would be OK with that. It's not like in the M5 where it is a digitally made sound.
The M550d has audio enhancement, and it really sounds good on the inside (and that's a diesel).