Has anyone ever bought from Audio Liquidators

You should read the company's warranty policy thoroughly. Since they are not authorized dealers for what they sell, warranty on any products they sell would be handled through them to a third party servicer. So in addition to the other risks mentioned above, there is no manufacturer's warranty with their products.

Never would buy from these guys.

I was looking at their subs and I see they are selling the REL S-3 for under 1600.00. This sub retails for 2000.00. If they are not an authorized dealer how can they buy it cheap enough to be able to offer it at this price?

Call the police.  Seriously.  I've done that when I have a street address and asked them to pay them a visit.  The also can tell you if any police reports have been filed about them.  Yes, most police departments have better things to do, but on two occasions it worked.  One turned out to be okay, the other not, being a non existent address.

Check Music Direct, today they have the S-3 for $1500, and they are an authorized dealer.