Thanks. My mistake a straight 6. Yes the prices are dropping for the 2004 to 2005 X5s.
There are better priced 2004 4.4 X5 with better mileage too than the 3L ones.
If there are no major changes between the 2004 to 2006 then I guess the best option would be to look at the mileage and of course the history and then buy it.
There is a 2004, 4.4 with almost all the options apart from a Satnav for 13,000 Dollars with 104,000 Kms. The options include heated steering wheels and memory for steering wheel too.