I consider the following to be essential no compromise options that transform the X3 into a very capable fun SAV;
35i engine - 0-60 in 5.3 seconds - as fast as a Porsche Cayenne -
M Sport - Sport Seats - M Wheel and other M inspired tweaks – the standard seat is inadequate especially if you are tall.
DHP - I would not own a BMW without it – huge bang for a few $.
Tech/Nav - I'm not spending $50/60K to look at a Garmin.
BTW Premium Stereo - I have it and like it very much but I would not consider it essential.