What should I pay?

[bmarti13]

Hey guys,

Looking at a 2003 Boxster S with 38,000 miles.
Engine was replaced under warranty at 12,000 miles.
Grey on grey. Michelin P2 Pilot Sport tires with about 1000 miles on them.
Excellent condition exterior and interior. Top could probably be replaced as it looks a little faded. Some curb rash on 2 wheels, but not bad.

Having PPI done tomorrow, so if that checks out, what would you pay for this?
It is listed for $20,000.
Blue book is $22,600 for Very Good condition.

Thanks!