Here are some other options to consider:
1. You can trade-in your car and the dealer will add the negative-equity into a new payment plan. Depending on the dealer and the car, the dealer may have promotional dollars that will help buy down the negative equity. This may help you get a car with lower monthly payments.
2. If you are having trouble with your monthly payments, your financing company may be able to help by temporarily reducing your payments for a short period of time.
3. Ask the financing company if they will accept a smaller amount to payoff the car in lieu of voluntary reposession. If they do, you will be able to sell the car for less than you owe.