Tam I think you saw the TiSi 4.8iS sell over on bf.c recently. That would be fairly similar to your vehicle. Not sure what the final sale price was but he had it listed for around $18k-19k with 83k miles on it (but it was listed for over 2 yrs as well). I don't see big numbers for our E53's unless they have uber low miles. This has been listed for months, started at $20k (
2003 BMW X5 4.6is - Pre-Owned Inventory) One of the lower mileage iS I've seen in awhile. Hope some others chime in, but goodluck if you decide to sell it! Great looking SAV