CPO is not really going to be a factor, it expires in 3 months. The hitch is nice if you tow. If not, it's not worth much to the buyer. Even so, I used hitch is only worth $200 at most. New tires are an add and the stereo may have added value as well.

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'03 Carbon Black M5
'04 Silver X5 4.4
'04 MB SL500