Just wanted to follow up on this for anyone looking to install the Pioneer head units with the iPod control cable. I found that the cable is a bit too thick to fit through the hole the original poster pointed out at the side of the glovebox opening, but I discovered while working on how to route the cable that the opening for the glovebox light also gives easy access to the back of the stereo.

This isn't for the really faint of heart, but it's not terribly difficult and I got a really nice, clean install by popping out the light housing and taking my dremel to the back side of it to make an opening to route the cable through. By putting it on the back side, it doesn't mess with the aesthetics when you open the glove box unless you stick your head in the glovebox to look at it. The added benefit to putting it through the light housing is that the cable drops directly into the glovebox instead of routing around the side and potentially interfering with the closing action. Then I simply pulled the cable over to the stereo, hooked it up, and now my iPod stays securely locked inside my glovebox when I park.

When I first got my XFire I was planning on stripping out the factory audio system and doing a whole new setup. In the past 3 weeks I've done a new head unit (Pioneer DEH-P7900BT), bass blockers in the doors (scosche 200Hz), and the iPod cable that goes with the head unit. I could not possibly be happier with the results. Now I'm not sure I even want to bother with replacing the factory speakers and amp!