As I owned a 93 300 SE and eventually traded it in for a 94 S500 I know exactly why: When Mercedes changed the radio for 94 they changed the EQ curve as well. My first radio sounded like crap. There was hardly any bass response and tons of treble. The regional rep told me they'd changed the eq curve because customers were complaining that there was too much bass in the earlier Bose Beta stereos.

I went through about five different head units and 2 amps before I gave up. The stereo in the CLK sounds ten times better than in my S and I've got 3 more speakers and a larger amp.