My intent is to have a single connector, hard-wired cable that's ready to connect to the Karma when I'm in the car.

If you can even set up an aux-input on the factory stereo at all (the basic prerequsite for this to work in the first place), then I recommend just keeping a 1/8" cable in the glove box and plugging the karma's headphone jack into it.

That's what I do in my wife's car, and it works like a charm. No docking station needed. One wire, no clutter. Since the Karma playback lasts 15 hours, there's no need to connect power or anything else to it.

The Karma isn't a car stereo no matter how hard you try to make it one, so if you want a real harddisk MP3 car stereo, figure out how to the get the empeg in there in place of the factory stereo. Otherwise, I think you're going to too much trouble just to make a Karma car dock.