http://musicarnw.com/e92-3-series-coupe-subwoofer/
E92 Coupe Level 1 Add-a-Trunk-Subwoofer kit
This kit includes everything you need except hand tools:
- Plug-and-play interface harness
- 250-watt, fan-cooled micro-sized amplifier
- 12″ high-performance subwoofer optimized for small sealed enclosures
- The E92 OE-Look corner-loading enclosure with acoustic polyfill
- Mounting bracket and hardware (uses existing sheet-metal opening)
- Amplifier power harness
This is used but in excellent condition, with no wear. It sounds AWESOME. I have enjoyed this for the past year in my e92 coupe but I am getting ready to trade it in and need to part ways with this sub. It includes everything that came with it: subwoofer, enclosure, amp, wiring + taps.
If you want to pay the shipping cost, I will ship it, but it is likely to be around $100.