Maybe not what you are looking for, but I own both an E90 M3 and a Cayman R (3.4 DFI). While I love the cayman for the track, the power output and sound of the E90 is far more impressive than the R. Its not that I don't appreciate the sound of a Porsche motor running through its RPM range, its just that the BMW motor is so much more impressive in sound and speed with which is gathers speed.
Before the M3, I had an S5 and that motor was completely lame compared to the M3. It sounded slow and lethargic. Back then, I traded my S5 for a friends M3 for a day and the motor was what won me over.