Jsbail: Your questions are too general for may taste. I will say that loudspeakers bought used, are one of the "less sure" things you can do. I've done it, but only directly from the manufacturer, and I also sort of got lucky. IMO, People are much less likely to "go through" speakers for the sole purpose of trying several to see what they like, than they are to do so with electronics. That said, I have NO generalized impressions of "how the buying of a loudspeaker 'works out'", here at this site. I have purchased other items thru here with no real problems at all. However, I feel that trying to SELL something through this site is a real pain, you get tons of lowball offers and harassment, much of it from persons not in the USA, or even in an English-speaking country. I prefer another audio site when I advertise something for sale. Maybe that's just me. You want that troublemaker's name? I don't know the real one, but he called himself "chnupa". Anybody else hear of him?
