I've got those speakers and for that price, plus a receiver, it's a steal.
Understand that Mark has dealt in the hi-fi industry for decades. If he has those speakers, there is a reason, because he has seen many other speakers come and go!
If you are lucky, they are still there. Athena speakers are very good, but they never gained the brand name recognition they deserved.
If the seller had JBL or Klipsch (or even Bose), they would be easier to sell because most buyers recognize those names as established speaker manufacturers, but don't have the benefit of exposure to a brand like Athena.
He says he bought them in 2010 and only used them for 6 months, so they should be in excellent condition. If the grills are removable, make sure each driver of each speaker is working. you should be able to easily hear the tweeters, and resting a
light finger on the woofers, you should feel the vibration when the low notes are played.
You might offer $250, but go with $270 if he won't drop the price! Four towers and a center of good quality for $270 is absurd. Throw in a sub and receiver, and I feel sorry for the seller!
If you have a favorite DVD, take it with you. Something with some music would be good. Usually the intro to any movie has some music. Then check out the bass.