No. Were I in the market for another X5, I'd pay $12k. But, you might have to hold on to it for awhile to find someone like-minded. Some think the 4.6 is worth more than a 4.8, and some think it's the other way round. There are lots of 4.8's in your price range, though most won't have your maintenance history/records to back them up.
Take some good quality pictures that show how good the paint and interior are and you should be set. Also include a pic or two of maintenance records along with the manuals. Always gives me a warm and fuzzy when buying a car to get a binder along with it. You'll get your price, or very close to it. Good luck with the sale. Wish I was in the market for one. It would be a hard decision between yours and TMV's. But the imola would probably win out.