I'm relatively new to this forum and headphones, in general. In following the fora and the For Sale ads, I've come to a few conclusions:
1.Hearing and taste in audio equipment is highly individual. One person's audio nirvana may not be another's cup of tea, to mix a metaphor or two.
2. There is no substitute for you hearing the headphone in question in your system with your music.
3. It's hard to test phones before you buy unless you go to meets, etc and there is only so much you can get from reading and enjoying/dissenting in the fora.
4. You see so many headphones for sale either because a person buys without hearing, hears, but over time discovers that the particular headphone in question does not wear well, or they want to upgrade. In any event, there are many phones available for a reasonable price. Once a new headphone is purchased, it is "used" and the original purchaser typically takes a loss on it. Once something is bought used, it's value, if it stays in good condition, does not decrease much in value. The lesson, of course, is to buy used and try a particular phone. If you like it, Great! If not, sell it for a minimal loss. In the end, you can usually find what you want at a reasonable price if you are patient, try it, and keep or sell it, and get out financially unscathed....almost.
5. Bottom line...Try the phones you want.
6. I try to do this and it seems to have worked fairly well. There are so many varieties to taste and enjoy!