My advice on buying used speakers: buy local or make sure that the seller has the original boxes and foam packing. Only buy from someone with good A'gon feedback who either posts pics or emails you some. Good communication is a must. If a seller really wants to make a good honest deal, you should not be waiting around for a response to your email.
I bought my last pair open box from audio advisor, I get a full manufacturer warranty and they were half price. I'm thrilled with them. There was some hidden damage, but audio advisor took very good care of me. My experiences buying from A'gonr's has also gone very well. The used amp I bought started blowing rail fuses, but worked flawlessly for 6 months before that happened.
I cannot stress enough the importance of having the original packaging with the original foam inserts for heavier equipment. The box my pre-amp was in got practically crushed by UPS. Not really the sellers fault, he told me he didn't have the original packaging but would double box. He did, also wrapped with bubble wrap and filled with peanuts, which probably saved the unit; the box looked like it'd been run over with a forklift. the foam inserts would have better protected the pre, which was luckily undamaged.