What is his contact information and do you have copies of the payment you sent him. If it clearly shows his cashing you payment and not sending the product then you can file charges on him from where ever your at.
I hate to say it but if a guy is still waiting for a $500.00 nos system I don't think your motor is on the way.
By posting his real name and address, phone number and anything else may have more power then one would think.
Right now he is hidding behind a screen name and telling you B.S.
I would love to look him up and see what all he ahs been charges with and see if he is on probation now. Nothing like taking someones freedom to get them to pay up.
It's time he is put on public display.... for what he is