Too good to be true?

I have a pawn shop a few miles from my home. It is just a dingy old place. They have recently aquired some REALLY high end audio equipment, $6-7000 worth of speakers and amps. This guy doesn't know a woofer from his elbow. Is there a place I can go and run the serial #'s somewhere and find out if this stuff has been stolen from someone? For that matter, buying on a site like e-bay? How do you know what your getting isn't someone elses loss?