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
Spare Tire Well Speaker Box Sub Subwoofer Enclosure 12" Ported – AK Audio
Builds: 350Z Spare Tire sub Enclosure Part 2 | AnthonyJ350 - YouTube
JBL Stadium BassHub Passive sealed enclosure with 11" dual 4-ohm voice coil subwoofer — mounts to hub of spare tire at Crutchfield