Could you be more specific pls about your install? How did you sort out front speakers and amplifiers? Why did you choose slim mount depth subwoofers?
Anyway I believe your speakers deliver good hard back massaging bass with decent sound quality. I previously had a couple sealed boxes used to the tight punchy bass that such an enclosure provides. So you claim the port on your enclosure it's something like (a low noise design) and you don't prefer little boomy sounding because you listen mostly rock music?
Anyway, do you have some previous car audio installs even non Bmw? We can make new tread-previous car audio installs. I have couple pictures but is non Bmw install, I don't want drive admins crazy.