I tried carmax, carvana, and local dealerships (and tesla trade in). Tesla's offer was lowest, then dealership, then carmax. Carvana was the highest offer and we purposefully scheduled the pick up after the Tesla arrived so we had a car while we are waiting for the ppf to get applied to the car.
I think all in all, Carvana beat carmax by like 2.8k or something which is significant when the car is only worth 18-20k to begin with. Only downside is I have to wait a few days after they pick up before I get the check deposited into my account and due to timing, I will have to make a car payment on it this month and then get the money back from the bank later. Slight annoyance, but it is what I have to get done.