I wonder if David is beginning to miss Coda? It really looks nice. On my 86 300sdl I replaced my rear speakers with some factory speakers from a 88 560sel. They have the 6 inch speaker and two midrange/tweeters mounted on them. They angle in different directions and they have really changed the sound in the car. They fit under the factory grilles also. If you can find some on E-bay, I feel they are definitely worth it.
I also added an amplified subwoofer in the trunk, and it has really helped the bottom. I kept the factory speakers in the dash but added a pair of Volvo tweeters ( from a 760 Turbo ) and they all fit under the factory grilles also. No extra cutting needed. My sound has improved drastically.
Oh, my head unit is an older Panasonic with 50W per channel times 4. Alas, no Bluetooth or Ipod input as of yet.

In my 67 Beetle, I installed an old Becker Europa II with an Ipod cable that plugs into the DIN input slot in the back of the radio. It plays AM/FM stereo until I plug the ipod into the input jack and then it plays my Ipod tunes. Plus, it looks like it belongs in the dash of a classic old Beetle.

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John
1986 300sdl
1985 380se