I would highly recommend getting a cpo'd x5 from a dealer. while you may pay a premium for one of these cars, its insurance that i'd rather have. I also purchased the extended maintainance plan. the entire cpo purchase process is quite painless and bmwfs usually has good interest rates when you buy off their cpo inventory.

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'90 E30 M3
'05 X5/3.0 Sport (E53)
'03 540i/6 M-Sport (E39)
'91 325i/5 Sport Package (E30)
BMWCCA #360858 SCCA# 374179