I would see if you can get a copy of the latest Black Book -- that will give you the no BS "actual" value of the car (auction value).
If the 2013's aren't listed yet, you can generally figure out the ball park based on depreciation between model years.
Wave the black book in front of a dealer and see what happens
Also, in working on the OTD, ask exactly how much is profit from nonsensical dealer fees and what not. They are already geting 3% holdback and possibly some incentives.
Read over the new car buyers thread on here -- it's really helpful.
Good luck!