First...does he still have this stuff?
And, yes that sub is "over priced" if you were buying new...but you aren't. I think(considering what you are getting it for) it compares very nicely to a BIC H100/F12.
$600 is just about right.
Besides, it would be very simple for you to get that sub home, purchase a BIC H100 or F12 from Amazon, try them both out...then either return the F12/H100...or sell the Klipsch to recover what you spent on the BIC.
Lava(being the only other one in the same price class) has a 30 day home trial. If you return the sub, all you are out is shipping back to them...