I need some advice. I have a 2007 BMW 530xi in excellent condition. Its been well maintain, every service expected and then some. It is now at 106,000 on the odometer -- all highway. I recently, came across a 2010 528i with xdrive with only 20,000. Thinking of making a trade. But after test driving he 528i, I felt that I was giving up a lot for a younger ultimate driving machine. What should I do?