Hey Jim,
I would like to add some comment on the depreciation factor between the 535xi & 550xi. As you know, the biggest depreciation of any cars will be in the first 3 years of ownership, therefore, if you are going to keep the car for about 3years +, then the resale value between the two may not be so significant.
For example, after 3 years, a 535xi may retain about 52% of the orig. value wheras a 550xi may retain about 48% of the orig. value (lowered because of the V8 factor ... gas guzzler !)
But you have to consider the FUN factor involved
