I made a trip to the local dealer and he had a few nice used X's there. Say using KBB or the like how much below do I offer? I am looking at a really clean CPO 2005 X5 3.0 loaded up really nicely. Is it a buyers market??

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2009 X5 3.0i, 2005 Volvo XC70, 2011 VW GOLF TDI2002 Jetta 1.8t, Ford F250 Diesel