I installed my sub and AMP today. I used the thin black (more like super thin) wire behind the rear passenger seat that VP Electricity mentioned. It was very easy to locate thanks to those photos.
I was a little nervous to splice into that wire because its very thin. But I would rather do that than take a part my dash.
I didnt have a helper or the time to take pictures, but VP Electricity clearly pointed out a easy and close location of a remote lead wire.
I used Technics harness, a LC2i, 2 10" JL subs and a mid size box up against my reat seats. It sounds nice, But I want a single 12 " in that pretty sub box TECH has in the side of this trunk.
Thanks again VP!
///2013 AW 6MT E92 ZCP M3/// Black 359M Wheels/BMW Performance Carbon Fiber Spoiler and Mirror Caps/Arkym AeroSport Front Lip/Turner 15MM Spacers/LUX 8 LED Halo/IND Gloss Black Grills, Gills and M3 Emblem/30% 3M Tint/BMW Interior LED/MusicCar Subwoofer Enclosure/JL Audio 12" W6 Sub and XD600:1 Amp/Euro Sunglasses Tray/Ceramic Coated Megan Racing Exhaust/AFe Dry Air Filter/RPI Intake Scoops/Euro MDM/Feature Coded.