I don't believe there is. However, getting in the dash and removing the stereo isn't too difficult so you can to be sure.
The Xs never had a changer option because there was no convenient place to mount one - at least from an OEM standpoint. That's the reason they offer the 6-disc, in-dash changer stereos. The only reason it might have the output would be if the same head unit was offered in other Nissans, ie Maxima or Sentra, and the changer was an option on them. But, again, I'm just not 100% sure.