I've been considering doing something similar with my 1995 840. The audio system is not very impressive for a car of this type. I want to keep the factory head unit and 6 disc BMW changer in the trunk.

Any suggestions on an upgrade plan? Has anybody had a particularly good experience with speaker upgrades and/or adding an amp to the factory head unit?

Finally, I'm having a heck of a time finding a CD magazine for the changer. Even the dealer can't find it. Again, it reads "Type A" on the sliding door of the changer. Anybody know what magazine I need?

Thanks,

K/
I actually wrote this letter for another reason but last part may be interesting for you people.

Thanks!
In sweden we have a brand called MDS.
I previously had a 520iA in which I installed a MDS system. It already had a Pioneer main unit and a Pioneer 6-changer in the trunk (looks exactly like the BMW 6-changer). This was baught 1991, pretty nice to have a CD-changer 1991. Anyway, this system was running on the standard BMW speakers and they are not very good. I bought a system from MDS last year consisting of 4-channel 600 Watt amp, kickpanel speakers 4 1/4" if i remember correctly, tweeters, filters, a 12" sub-woofer and some cables. The main unit supplied audio signal through low level signal cables to the amp in the trunk which in turn supplies audio to the filters in the kick-panels through speaker cables and those in turn fed the kick panel speakers and tweeters. Also, the remaining two channels on the amp was bridged to form one 300W channel for the 12" subwoofer in the trunk.
I did the installation myself and the hardware cost about 600 USD. The sound quality was great with lots of bass. I also tested with a 21" sub-woofer. It filled the trunk completely but the bass was nice.

Now, for the BMW 850 I wasn't very interested in doing a big installation so I bought kick-panel speakers, filters, and tweeters. The kick-panel speakers was easy to change.
The filters is laying loose behind the speakers. There are some empty space there. I wrapped them up in soft fabric so they won't make noise. I checked the colour codes on the wires in the kick-panels and figured out which wires went to the speakers and tweaters respectively. I cut the speaker wires, connected them to IN on the filters. Connected the speakers to the low-out. Then I cut the tweeter wires and connected them to the high-out.
The tweeters placement was a bit complicated. I cut out the original tweeters from the plastic braces and glued the new tweeters in place with a warm glue pistol.

The resulting sound is crisper and more alive. The BMW original was dull with sloppy bass and dull treble.

The hardware for the 850 cost me about 170 USD. Not much I think. It was not the low-end system they had but of course you can always go higher.

Hope this helps of you are going to change your speakers. I think you should. BMW original sound is bad.