These guys make decks that are supposed to fit nicely into the factory dash. I know there may not be a direct fit for the XJ, but I'm a Pandora Radio addict and Alpine's CDE-123 deck just doesn't have the interface I was looking for...
http://adventproducts.com/oemultimediasolutions/

Thought about getting a GPS / Radio / MPs /etc for the Cherokee, but seem way too big to fit in the stock XJ location... plus, pricey to be run on the trails...