You are probably going to get raped on the sale to carmax. SAN QUENTIN MAX SECURITY PRISON azz rape. I knew a co-worker who needed to sell his car and Carmax gave a low-ball offer. They know people are pseudo desperate when they want to sell to carmax. Carmax might buy it from you for $9,500.

Go ahead and ask though.
You are better off selling the car on your own. Tell the prospective buyer there is still a lien on the car. To get the lien off the car, you need to take the money that the seller gives you and pay off the lien, then the title gets released. You pull a double-reverse whammy on the deal and you'll get strung up by your balls in civil court. Say you sell it for $16,000. You cash the check, pay the bank $10,000. You keep $6,000. Take that and use it towards your next car or whatever.