Found my Black Cherry Z. Dealer won't budge...help!

JohnsZ

I found the 370Z that I absolutely love. A 2010, 370Z Touring, Sport/Pkg, Black Cherry, 13,500 miles, Nissan Certified, and in excellent condition. I already test drove it and it runs great. The dealer is asking $28,700 for it. I have a 2012 MazdaSpeed3 with Tech Pkg with 4,500 miles on it that they offered me $19,500 for which I think is very low. I owe $15,000 on the MS3 which cost me $27,000 for. I can only put down $2000 at the most as down payment as well as the equity from the MS3. Bottom line, I need to get my payments under $300 per month but the dealer is not helping me. Should I walk away and forget this Z or continue to work with them. The car has been on their lot for 2 months. I love the car! Please advise! Thanks!