Great speaker sounds terrible in my room?

Am I correct in understanding that you you went from from a normal listening environment with wall reinforcement to a near field set up?

If so, the situations are bound to sound totally different, and you cannot expect similar results. Moreover, only some speakers sound good near field pulled into the room. You have to decide how you are going to listen and pick your speakers accordingly.

Changing absolute phase, as suggested may help to a certain extent, as your amplifier setup may differ in polarity to the dealers. But you will always find that a certain percentage of your music collection sounds better the other way round anyway. Having a phase reversal switch can come in handy.

Phase and polarity are not the same thing! Polarity is a function of positive and negative wiring, while phase is a function of time.

If they were from a store sale, call the store. Or return them.

If it was a private sale, then offer the fellow, or woman, a dinner (or something) to help you set them up.
(If they did it once, then there is proof that it worked for them.)

Unfortunate.  The same thing happened to me several times.  I have said many times that in a domestic environment with limited placement options, it is a total crapshoot how speakers would work.  In my own home, a tiny pair of Harbeth P3s had better bass response than the much larger Model 30s.  Totem Forests and Hawks sounded horrible, but the Model 1s were very good.  Outside of finding a better placement, I don't think there's anything you can do.  See if the seller would consider taking them back with maybe a sweetener of a couple hundred for his trouble.  

It has nothing to do with the binding posts or any defect in the speaker. It is the interaction of the speaker in your room. If they sounded excellent somewhere else than you also can make them sound excellent. Moving them back just a foot can dramatically change the bass response but forget about getting much under 80 Hz with a 8" driver unless you sit a meter away from the speaker. Many speakers have boosted mid bass to make up for no low bass. A speaker that is flat might sound bass light. The best way to deal with this problem is with a calibrated USB microphone and a computer. Knowing is always better than guessing. This is true of any system. Finally, adding subwoofers with digital bass management is an incredible way of making little stand speakers sound like big Wilson's