What would be the best way to upgrade the stock MBZ sound system on a 2000 C230 Kompressor. Is there a speaker upgrade that can be done with out any modifications?

I do not believe this is easily accomplished. Your car has a Bose system in and it operates speakers on 2ohms. If you replace only the speakers you will most likely blow the head unit, or if that survives, then the new speakers will cook. I just visited my stereo guy this past Saturday to up grade my system in my 97 SL. He said he would not even work on it. I was informed that the ENTIRE system would need replacement and would be QUITE involved and costly. Soooooooo...it comes down to how deep are your pockets and how much do you want to dismantle your car. I even contacted BOSE directly and they informed me that there was no upgrade available, that what was in the car was matched for it. Also, Mercedes uses fiber optics in their stereo setups. Unless your "new" system would be compatible, you would need to do extensive re-wiring!!! Good luck..I will be watching this thread to see what others have done.