I have an 89 560SEL with the four speaker system. Someone had already "upgraded" the system with a Clarion headunit and a 2ch Sony amp running into the stock wiring and fader feeding the factory speakers.

I replaced the front and rear speakers with some average Pioneers, ran new wiring and installed a nice JVC stealth front head unit rated at 4x50.

This all sounds a ton better than what I had which already sounded better than the factory setup.

Matt.