BMW decision is based on a much larger scope (than what it being an M3, or called different), it based on BMW tradition of 6
Speakers: CDT Audio HD-42 comps--front doors (RAAMmat deadened), CDT ES-06 6.5" woofers--kickpanl Pods, Hertz EBX202R dual 8" ported trunk sub. Amps: Phoenix Gold RSd 500.4 (comps & pods). PG RSd 600.1 (sub). Power & Ground: 4AWG Streetwires w/RockFosgt RFDB1 distro blocks. Input: HU lineout--Kicker KISL RCA adapters--RockFosgt RFIT-6 cables--Audiocontrol Matrix--Monster cables--RSd 500.4--lineout Monstr Cabl to RSd 600.1.