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
CDT Audio HD-42 component, CDT ES-06 6.5" Woofers in Custom Front Pods, Hertz EBX202R Dual 8" Ported trunk enclosure. Phoenix Gold RSd 500.4 to HD-42s & ES-6.5s, and RSd 600.1 to Hertz EBX 202R. Audiocontrol Matrix w/ Kicker KISL line/RCA adapters. 4AWG power and ground wires w/ Rockford Fosgate RFDB1 disti blocks.