Don't do it.
I am an owner of 2000 RX300 AWD. I test drove both 2.5L and 3.3L X3. Not impressed! In fact, I couldn't believe the ride was so bad.
I like the look (exterior) a lot too. But, you definitely definitely need to test drive it before you even think about it.
The full story, it was a year ago that I bought my RX300, used. And, it inspired my friend to look at X3 a few months later. He had known the salesman well. The salesman was pretty busy, managed to get us started with the 2.5L. We took turn driving the car. We took some city road, some shape turns, and highway. We came back pretty unhappily. With the eager transmission, the power was ok, but not great.
The car felt heavy. But, the ride was rough. It felt like the car was put on springs without the structs. Feeling Boncy even just making a lane change. Felt much worse than an old Dodge caravan with the truck springs at the back, which my father had been driving. I am not kidding. Needless to say, handling was not great with all these bounces.
We went back after about 20 unhappy mins, switch to 3.3L. We test drove for about 20 mins, and went back more happily but definitely not great. The salesman was even more busy with the paperwork with client. So, we drove the car out again for another 1/2 hour. That's a bit longer than we planed. But, the salesman was still busy. But, it was alright. He don't really want to buy the X3. :-)
The first feeling with the 3.3L was Wow. The engine has much more punch, and the car doesn't feel heavy anymore. That's what you expect from a BMW. Alright. Comparing with RX300, it is definitely faster. (we later the same day went to Lexus to test drive a RX330. The X3 3.3L felt a bit faster than RX330 AWD. And, about the same as FWD version.)
The eagerness and the smoothness of BMW downshift make the car so much more fun to drive. On highway, on the 5th, once you press the gas hard, it immediately knows what you want, it smoothly shift 2 gears if needed. The RPM shoot right up from 2k+ to 4k+, and plenty of horses waiting to give you the torque there, and you're ready to zooo. The downshift is noticable, but very smooth every single time.
Both new and old version's of RX tramission was much more lazy. The upshift was always smooth. Downshift one gear was usually pretty smooth. Down two gear, about a quater of time you get a rough shift, while other times it was smooth. It really not too bad, but this unexpected roughness kills a lot of fun, when "you" are in spirited driving mode.
Back to the ride of X3, it was improved from the 2.5L a lot, but it was still not acceptable. I felt the body of the car roll a lot with uneven road. Say the road has a pitch on the left, and then on the right in 5 meter. You feel like you slide to the left a bit and the car tilt to the right... For handling, it also improved from 2.5L. But, it didn't feel that much like a car. You still got a lot of hint that you're driving a SUV with high clearance. It didn't feel as stable as the RX330 on high speed (90+ mph) either.
I never own a BMW, but had been the passenger enough of time to tell. It was not typical BMW at all. And, BMW is absolutely not ready for prime time of small SUV.
Even I like their tramission so much, it is still not a good car. I think they are not that many on the road for a reason.