I recently purchased a sound system for my 99 xj8. I'm determined to NOT mess with the factory deck so the plan is to have the deck new deck I just purchased installed under the console armrest. Has anyone else tried this approach?

 

If you plan on just installing a deck, I don't see much problem as long as you have the room in the armrest itself. The route I would take with it is to get a harness adapter that will plug into the factory harness from the old radio. Something like http://www.caraudioni.com/car-audio-...-v8-xj1-p-4954 . I would then extend the pigtails so they are long enough to run under the ski slope and into the armrest. On the armrest side I would unscrew the 4 screws that hold in the lining and remove it. I would then fashion up a piece that not only secures the radio but also screws back into the 4 factory holes from the liner. Plug in the radio, screw it down and you have done it. This means that no damage is done to the car and it can always be reversed at any time. I do not know if your car has the factory amp, and if so not sure how it will take to the new head unit. You are going to have to wait for others to chirp in on that.
Good luck