Re: Rear Bose speaker wire location
I've put some infinity 6x9" speakers in the rear shelf of my 1999 156 V6(with a bit of jiggery pokery you can fit them into the existing plastic speaker brackets on the back shelf). I too thought the rear door speakers were rubbish.
The speaker wires in the boot were active when I tested them, although I didn't use them as I have the speakers hooked up to an amp in the boot. The existing wires in the boot already have connectors on but if I remember correctly, it's not easy to tell which is +ve and which is -ve.
Just a word of advice - you will get better sound by upgrading the front speakers rather than the back. It's all about staging and the rear speakers should only really be providing 'rear fill'. A good quality 17cm component set in the front doors sound spot on (make sure you fit sound deadening material inside the doors to keep those annoying rattles away). Hope I've helped.