I'm not going to get into an argument about what nosier, but my 110" Harley with de-catted header pipes and 2.5" baffles barks with the best of them.
I have the factory Harman Kardon head unit but have upgraded to 7.25" front three way speakers with their 200w amp. At 80 mph I can hear my tunes just fine and my wife hears them from the back just fine.
I'm sure that the M3W has a bit more clatter noise, with the BB, belt etc, but don't count out a good set of speakers and an inexpensive amp. I'm thinking about $600 and you could have a system that's probably going to work.
I'll admit that I would be one of the first to add tunes regardless of the noise. I've been riding motorcycles for over 51 years and the ones with the tunes make me happy.
I'd suggest getting a good battery powered Bluetooth single speaker, maybe a Bose Soundlink and try it out. I have the portable Bose Soundlink and they put out some good sound. It would be worth a try to see just how loud you would need for a true setup in the M3W.
