Buy used, try them out, and if you don't like them, flip them. If you don't overpay you should be able to get most or all of your money back.
Headphones are a personal thing, definitely find out if the person selling is a non-smoker and consider buying a new set of earpads for them.
Headphones are a personal thing, definitely find out if the person selling is a non-smoker and consider buying a new set of earpads for them.