Ouch! This is going to hurt. The most expensive one you can afford.
The reason being the newer they get the better they are. The 2001 being the one with the bugs worked out the most, not all but the most. Watch out for the Nikasil problem for 95 and older. Look at
www.E38.org for answers to questions you may have about these cars. Research carefully! I have a great car but I know it can cost thousands if I neglect it a little.
Good luck!