I got it in Birmingham, AL at Stivers Ford. I started from Akins Ford (Atlanta) that quoted me close to that price. At the end of the year, Akins were advertising -6k$ on auto trader, it's now -5k$ but you should be able to get that price.
I did the negotiation by email over a 2 weeks period...
Last week end, I bought a Mustang 2016 v6 automatic for 20,090$ (26,000$ MSRP) before tax and fees, the total was 22,090$ OTD.
I had to drive 2h30 to get it since the locals dealers wouldn't sell me one at that price. I am very happy with the car and price so far.