Well...if you're looking to get Ferrari sound and aggressiveness, the restricting factors lie in the dual-plane crank and the headers. Flat-planes and 180 degree headers are what truly produce the "BRAAP-BRAAP-BRAAP", but you can get close if you're willing to drop a bit of money. It's my honest opinion, and JUST my opinion, that many of the loud exhausts (R1000 specifically) really disgrace the engine's tone by just amplifying the noise and don't get the true rasp that many others do. If budget wasn't an issue and you still want flat-plane, 180 degree header signature, you might wanna talk to Kriessig. I BELIEVE they are owned by Meisterschaft, but details are ambiguous at best. I'm sure they'll do an insanely expensive yet awesome solution that will a) bring the police to your door often for peace disturbance, b) have a degree of badassery unattainable by most anyone else and c) be worth every penny as EVERY person turns their head when you push your car. It seems that they no longer have a site though, so it might be difficult to contact them. I think the Meisterschaft sounds beautiful and does the engine justice, and if you want to make it louder than that, you can always run test pipes and a good set of high flowing headers. However, if you can manage to get in contact with Kriessig and also drop around $8k or possibly more (hey, anyone can dream), you can sound like this...
I think your car might need to be pretty effin' fast to do an exhaust like that justice though!
Anyways, beyond my rambling, I say stick with the Meisterschaft. And if you can even begin to consider a Kriessi(e?)g who once again I believe Meisterschaft owns, I'd get in touch with someone on BMW ///M forums. You'd have something that would probably be one of a kind. Like I said, wishful thinking for most of us
. Good luck!