Since Klipsh as acquired Energy which also owns Athena I don't see much future for Athena. One thing you have to consider is that you do not have any warranty on used speakers and therefore the price tag must reflect this.
As far as Polk, if you are not in a hurry, you should enroll with newegg''dot''ca newsletter and maybe wait for the 70s to go on sale. I've seen them go as low as 149 which all considered is a better investment than the 60s as it can provide a much more complete frequency range for music and HT (mind you with HT a stand alone sub is always welcomed).
Happy shopping
TK