I would say that is a fantastic deal. I have a black pair of KSP-400's and they don't sound like any other klipsch I have listened to. I paid a similar price from someone who just wanted to get rid of them because they were moving. The weight of them is rather surprising....very solid build.
They are quite a different animal.... but if you are selling-- unfortunately not alot of people recognize the value of these so the resale doesn't seem to be that high. But if you're buying....and you look hard enough, you may be able to find a pair at a very reasonable price. My opinion is that the price paid on these is far below the value (in listening quality and performance). Those sealed 15" subs are tight and hit hard and with the higher sensitivity,along with sub amp onboard...they don't take much input power to sing.
Once they are dialed in, I think you will really enjoy them. Congrats on the purchase!