If you go for the used market you are limited to the reviews of opinions from many but are not able to actually audition how they sound for yourself. That's where going to an audio dealer that may have the components you have interest in and will fit into your budget comes in. Audition amp and speaker combinations and decide what sounds best to you. If the dealer may also have the sources you prefer audition them as well.may also have the sources you prefer audition them as well.
I recommend the used market for speakers, but only if you shop locally. That gives you a chance to listen to them and decide if they are right for your ears. i used Craigslist, and auditioned at least 20 different speakers before I found the ones that "spoke" to me; if the seller won't let you audition, just thank them and move on. Also, pick a selection of 3-5 musical pieces that you are very familiar with, that are well recorded, and that, as a group, give you a fairly broad spectrum of musical frequencies, dynamic range, acoustic vs electronic, and vocal vs acoustic. Take those pieces with you to every audition (I recommend on CD), and always play the same ones. If the seller has a high quality streaming account, you can always look up the songs on that, but if he or she doesn't, you won't be stuck listening to whatever they want to put on. Finally, there will be times when you are listening to a good pair of speakers but they don't sound their best -- it could be a bad fit with the electronics, or poor room treatment, or whatever; don't sweat it -- just accept that that SYSTEM wasn't what you were looking for in terms of sound quality. If you do enough auditions, you will eventually find a few that sound great, and you can choose one of those pairs of speakers knowing that, if you do a decent job of matching electronics and room treatments, you WILL like the sound. Enjoy the hunt!