If you decide to go used, I suggest engaging in a back and forth with the seller over some related matter--or even the weather wherever the seller is. Then decode his responses in terms of what kind of personality you're dealing with. Get a savvy friend to help. You can tell a lot from a fairly ordinary conversation.
To me, buying used is much more about who you're buying from than anything else. One guy I bought from punctiliously pointed out the very minor cosmetic flaws, working hard to get them to show up in photos. Then when he discovered he'd failed to notice a couple, he knocked $200 off the sale price. Before that, we had a nice chat about what speakers he was moving to, his wife's pregnancy, etc. That was my answer about whether I could trust him.
Of course, this only makes sense if you know what the speakers will sound like and that's exactly what you want. Other than a few semi-guaranteed to sound good brands, taking a chance--from internet research alone--that you'll like a given signature sound is risky. It's worked for me, but I'm sure others have been sorely disappointed.