If you don't want to install the empeg and want to keep the stock stereo in order to make use of the sound upgrade package, you can get a cable to connect your Karma to the CD-changer input from here:

http://babelfish.altavista.com/babelfish/tr?doit=done&urltext=http://www.misterdotcom.de/smart/Shop/Shop/kleinteile/kleinteile.html&lp=de_en&x=34&y=9

I've been using the second one on the page with a Riot and it works very well.