I've never seen any postings of all the speakers that are in the W124 becker 1432 system (sedan with door speakers). So I took a few while I am in the process of removing an interior. Also thinking about what to do on the new 400E when I put in the grey interior.
speakers - door is 2 Ohm front is 4 Ohm (wrapped with additional coil and component - cap?) rear speaker has 2 integral tweeters (never heard that noted)
amps in the trunk
So head unit on the new 400E was replaced with a Sony. My thought is to replace the fronts with some Polk db401 speakers I have kicking around. From looking through this list it looks like I can power rear and door speakers - leads for rear from head unit to console fader and set fader full rear.
May look at getting some 5.25" Polk's for the rear as well, either db521 or db5251 where I could mount the tweeter in one of the original locations. Leave the door drivers as is.
Paul