If the Vibe Slick is the one I'm thinking of with the Hi/Low switch on the end and the fan on top, and you are recoding, please don't use an LOC. Buy a short set of twisted-par RCAs and hack them.
There is no MB Quart BMW kit in the states, so I don't know what you mean there. Ground Zero doesn't have an importer any more either, and I never saw anything from them that fit there. That is a lousy sub location and you need midbass from them. Lots of threads on that.
Musicar Northwest Portland OR musicarnw.com
Musicar Certified Sound for BMW