first of all.... I think you got a 2003 instead of a 2003.5 since you have a roof rack. I may be wrong on this but correct me if I am....
My P5 MSRP is $19625 with leather, 6CD, ABS, bling-bling wheels, side-airbags.... I managed to talk it down by $5K ($2500 rebates + $500 rebates +dealer...