I just tried putting a set of 20W Boss 4" speakers into the Kickpanel mounts on my 1970 280SL. The speaker magnets were too large and almost touched the steel fender panel, and they also distorted, as the volume needed to be higher on my Becker Europa 2 which only puts out 7w per side. I finally caved and called Becker Audio in NJ (Tom) and got the stock speakers made in Germany ($100 per pair, for speakers only, not the black housings). They are much better, fit better, and sound great with the radio. If you want to stay pedigree with the car, This is the best way to go, after my research and trial and error. Some folks are putting amps in the trunk and modern speakers, but I chose to stay as close to spec as possible. I bought the 3.5 mm jack that plugs into the DIN 7 connector in the back of the radio, but the volume is low when I plug in my MP3 player. So distorts when I turn the volume up to 80+%. Not sure how to address. Good Luck.