With that amount of money being spent on the car up to this point, it seems like many problem areas have been fixed, including the transmission, which is great. As an added bonus, you have the entire service history of the car in hand, which should set your mind at ease even further. If the car is well kept cosmetically, and at 18 grand with that mileage, it probably is, I'd be tempted to go for it. If it were my decision to make, I might consider a used car warranty just in case, but I don't think it's necessary. The X5 is a very well built vehicle with a robust drivetrain, designed to be driven-that I'm sure you already know...

I bought our '03 4.4i with 71k miles for 18K in September. It was a one owner car (bought with cash) that lived a pampered life in San Francisco and Beverly Hills. The interior has very, very little wear and it drives like a tall sports sedan. In the rain, on a twisty, vacant road, one can slide the car around and steer it with the throttle, I kid you not...

One thing most folks might not realize is that despite the differences in design and power output between the M62 V8 (00-03) and N62 that came in the 04-06 cars, the acceleration numbers are virtually identical, the pre-facelift 4.4 being a few ticks faster (according to Car and Driver). The car you're looking at has 290 horsepower vs 315 in the later car and a 5 vs 6 speed trans. The full VANOS on the N62 and the 6 speed auto likely contribute to it's better fuel economy ratings than the earlier car.

The styling differences follow facelifts and other changes that took place at the same time in the BMW line (E46, E38-E65).

If you like this particular car, the color combo and options, then DO IT! The X5 is insanely awesome.

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2003 BMW E53 4.4i Titansilber/Black
2008 BMW E90 328i manual
1972 BMW 2002 std Colorado Orange
2003 Audi TT 225 Coupe