For those of you who want more bass but don't want to sacrifice your spare tire or hatch space, I highly recommend this spare tire mount subwoofer : r/GolfGTI
Amazon.com: Cerwin Vega 600 Watts Active Spare Tire Application Subwoofers Series (VPAS12ST) : Electronics
Anyone ever set up a spare tire subwoofer? : r/CarAV
Volkswagen VW Golf Fiberglass Box Installation in Spare Tire Well | Explicit Customs
Sennuopu Car Spare Tire Active Subwoofer Built in amplifier Class AB 1 – Sennuopu Audio
OEM Audio Music System Under Seat Subwoofer Powerful Active Speakers 500W Car Audio 12V Dual Car Spare Tire Subwoofer for 15/18 Inch Wheel - China Pioneer Subwoofer, High Power Subwoofers | Made-in-China.com
JBL BassPro Hub | 11" (279mm) Spare tire subwoofer with built-in 200W RMS amplifier with remote control.