Jordan,
Give him some time,he might have some kind of emergency.I have alot of experience on audiogon and from his ads.I think its too detail and most scammer do not like to take an effort to describe the unit in detai,and also I dont think he would pick a BBX as an item to scam people.usually it mcintosh or B&W .why dont you call him and leave a message on his phone and tell him that you are going to report the USPS money order is stolen.If he is smart,I am sure he'll call you right back..I am having my finger cross for ya.