Forget Crutchfield for drop in dash speakers. Here's some info for direct fit speakers - W124 300TE Speaker Replacement on the Cheap! - Mercedes-Benz Forum . There's also these - http://www.amazon.com/Brand-Cadence-Zxs-120-Speakers-Watts/sim/B000PTRFZE/2 - which drop into the dash openings after you push insulation aside. They worked very nicely with 5.25" MB Quart separates in the rear deck of my '87 300D (no door speakers). This place might still have them - http://www.lightav.com/car/cadence/cadence_zx_speakers.html .

Sixto
MB-less