On my '94 E320 W124 I just upgraded my factory stereo to an excellent genuine OE Mercedes Benz single disc CD player - I bought it brand new from Ray at Perfect Audio. It is called the Audio 10. The sound is simply incredible...it will blow you away trust me on that, it is made for Mercedes by Alpine under license.

I paid $400 for it and bought it off eBay. Ray does have hos own website and you can buy online there as well. I will look for the URL for you.

Installation took a few minutes and Ray supplies the keys to remove your old stereo and install the new one. You may need a harness adapter as your 300E is a little bit older.

I had to take my car to the Benz dealer the other day and the Manager, was blown away with the Stereo as he has never seen one like that in a W124 or any other Benz, as the Audio 10s were only available in Europe (Ray imports them and then has them re-callibrated for the U.S stations). It was pretty funny, he kept going on and on about it and where I got it, who installed it, how much did I pay for etc etc....I got a good chuckle!

I am not into the fancy LED, flip around and gymnastic abilities of the new disco ball looking stereos in my Benz so I opted for something classier with parallel sound abilities.

Hope that helps.
Yasin