I have a 2005 C230 K (I love it! It's my first!) with the Audio 20. I wanted to put the factory sirius in it (I already have an after-market unit I want to get rid of). The data card for my car has a line item on it "531 Sirius Satellite Radio for USA Preinstallation", so I'm thinking that it's compatible. The dealer says that since it does not have a sat button, it's not. Is this correct? Do I have to replace the head unit?

I downloaded the installation instructions for my car from startek and it looks like something I could handle easily. The part number in the instructions is "B6 783 0051"

I've seen prices on this forum from $600 - $1100 for the unit (not necessarily the above part number).

Where can I get the best price for the above unit? (and actually get the unit!)

Thanks in advance, Tom