There's nothing particularly special about upgrading the stereo in your Mercedes (other than the weird size of the speakers).

And there's noting wrong with the system that replacing every part of it won't cure either.

Add tweeters to the front door panels, add a subwoofer to the trunk, upgrade the stock speakers and maybe add more rear speakers, add a honking great amp and you're good to go.

Use 10 gauge wire to the amp and 18 Ga wire to the speakers. I've smoked the original factory ones with a decent amp.

Richard Sexton