The 2000 C230 contains its very own amplifying system, much like all of the mercedes benz's of its kind. I have a 95 220 and a 99C43 I have made both adjustments on both vehicles, including the head unit. Some say you can not change the head unit but i was able to; as well as the speakers. One manufacturer that does make fitted speakers for Mercedes is Nakamichi, those will fit quite well. But all other factory models will not, such as bose, kenwood, etc, etc. So this is your new venture, the cutting and wiring. I replaced my front side panels with 3x5's and added tweeters underneath the briarwood. The rear side panels contain 6x9 and one 12"subwoofer from MOMOM through a plexiglass plate behind the back seats, also included are three 4 channel 500 watt amps, for one set of tweeters and 3x5's, two 6x9's and one for the subwoofer. This process was actually the cheapest way for me to go, and spent close to 11k for both vehicles, but it does sound very good, much like a theatre or even better.
You can email me for pics if you wish to see.
Chris.....Hope this helps