Replacing 525it with X5 3.0--Please Help

[raysay]

My wife is making SUV noises again. She has a super nice '02 wagon w/31K miles, and wants an X5. I need to be under $30K, and there appears to be a fair number of X5's in the area w/ sport/premium/xenons/under 40K miles that fit. Are the problem areas for the E53 very simialr to her E39? She has had zero problems, but I keep hearing that the E53 is a bit more of a problem. She is happy w/ the power of her 2.5L (184hp), so I assume the 3.0 is enough power for her. I drove a 3.0 w/ 18's and sport and the ride felt a bit choppy, while the sport on her wagon is a very controlled comfortable ride. Are most of you happy w/ the 3.0, or is the 4.4 the way to go? Is it smarter to pay a bit more money, and go for an '03, or is it the same car but a year newer? Any and all feedback is much appreciated before I go much further in fulfilling the wishes of her ladyship.