Yeah, I definitely wouldn't drop $600 on a stock system. That's just what I was quoted at fordparts.com. However, I did see some used ones at a very reasonable price (~$100 or less) and would like to give that a try. They just don't match the part number 100% though, so I want to know what differences I would expect. For the time being, I'm not too worried about durability of the cd changer, since I very rarely use it anyway.
I also remember seeing somewhere that the audiophile units have an extra port for the subwoofer, could someone remind me of which one that is?