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
VW Golf/GTI MK5/MK6 Uberstealth Under Trunk Custom Subwoofer Enclosure + MB Quart Subwoofer | VW Vortex - Volkswagen Forum
How to make a CUSTOM FIBERGLASS SUB BOX! | MK7 Volkswagen GTI BUILD - YouTube