1. Go get them appraised at CarMax.
2. Get your payoffs from the bank.
This will help you find your negative equity.
Once you know that you will be able to see how much you will have to bury in a used car sale. Or, just keep them and pay them off as fast as you can.
The problem with buying a couple used cars is you will be paying sales tax again (depending on your state and whether you buy from an individual or not). Or there may be fees you will be paying for too at a car dealership. So before you do that find out what you will be saving in insurance and yearly registration to decide if that makes sense.
Boardmail me if you would like to ask specific questions. I am not in sales, but have been in the car business for 25 years in various positions.