Bose subwoofer?

Fountainhead

HI T_R_J,

If you search there is one article about a guy who modified his bose wheel sub to accommodate an external amp, therein he describes the pinout of the plug you found in your car.
BAF can explain further your options, most likely just running 12V from your battery to the trunk, then using an EQ to flatten the emphasis from the BOSE preamp (- if it's emphasized, not sure haven't measured/swept sine thru my system yet), then attach a new amp with a sub. There again are several threads here in the audio section where folks actually build subs that fit in the mag spare tire cavity and they are very satisfied with the sound.
PS: The "What to know about BOSE" thread actually has a lot of information about the BOSE system, some of it's anti-bose but that's everywhere, sort of like "anti-apple" etc., but the article does have useful info about alternative approaches to obtain the "urban" sound from your system with a BOSE Navi/Headunit. Your options are very limited though.
Happy Hunting!