15K down makes you very attractive for finance. Are you upside down on the two other cars? If not, just sell them privately or see if you can trade them in.
If you bought a 35K car with 15K down minus fee's you are only financing about 23.5K that puts you at a 67% loan to value. That is not much of a risk for a lender.
Are you in the service? If so use that to your advantage.