It is definitely worth replacing the speaker wiring. The stock wiring uses a chassis ground, which is probably playing havoc with your tuner. The factory amp is crap, just get rid of it. The Blaupunkt should have enough power for your speakers without a seperate amp, unless you want it really loud. I also have the Toronto, with new wiring, stock speakers, and a bazooka 6.5" 150w powered sub in the trunk (hung from the underside of the package shelf). There are no holes between the trunk and passenger compartment - plenty of bass gets through the vents. All of the wiring is under the carpet, just pull up the kick panels and lay the wires along the edge. The wires run under the back seat, and through the existing hole into the trunk. Looks perfect, and you can't even see the sub when you open the trunk. Sounds great, though it is not painfully loud.
All:
Just wondering what you have done to improve the stereo system's on your E28 M5s. I am currently running a Blaupunkt Toronto with a set of MB Quart components in the stock pods on the rear parcel shelf (custom installed myself). I am looking to do a full custom job though (replacing the stock amp, all the speaker wiring, adding aftermarket amp, EQ, custom sub enclosure in fiberglass, replacing the front speakers etc.) and was wondering if any out there have done this or if they have pictures of it. My main question is: how hard is it to unwire the stock amp (in the trunk on the left side under the parcel shelf) and put new speaker wiring in. How much will I have to tear up the interior to do this job? Thanks for all the help/opinions.
-Josh C