I went from an E39 540i 6-spd to an X5. Great car, but the trunk space is very small compared to my old E34, in fact, it's not much bigger than my E46 328i. However, that being said, it's a great car otherwise. You should be able to find an '03 with an M body kit relatively cheap. BTW - you could step up to an '04 545i 6-spd for a few bucks more and get another year or more out of the CPO warranty.

Good luck with your sale!