You might need to tell us more about your in-car solution. Are you currently running the iPod through your head unit? If so, are you running a line out of the headphone port, or are you using the dock connection into the head unit?
I have my iPod connected through the dock connection to an Alpine head unit. I've thought about trying a dock to see if it works, so that my iPod isn't just sliding around in the glove compartment, but haven't gotten around to it, and don't really care to spend the money. I don't imagine too many people have put a dock in their car, so that may be why you're not getting (m)any responses.