You're in the ballpark but you should be able to do a little better.
Edit: I'm assuimg the car is still being sold new even with the 500 miles. If it's being sold as used (previously registered) you should be able to do much better.
From my experience new cars at the dealer with a few hundred miles on them were ususally driven by the dealership management as their take-home cars. These guys drive to work and back like the rest of us, and for the most part it's unlikely the car was abused. The extra miles should be worth something in the deal, however, like accessory or maintenance credit (ask for something specific you are interested in - example: oil changes).