I really didn't want to post about this but, I have to.
KEEP THE MONEY!!!!!
Its a principle thing. I understand times are hard and shit happens but, that is something you should of thought about before you put money down on something. Espeically something like car audio which IS NOT a necesity.
On the flip side of it. Don't be dicks about it either. Aplogize for not being able to refund the money but, if he wants to find a buyer for you to make up the difference they lost on the deposit plus the original amount you were asking for, be wiling to work with them. I mean after all it is an SMD brotha it sounds like the deal went bad with in the first place.