If you purchased a HUGE amp to power those, it would be retarded loud. If that's what you want, go for it.
As far as what to pay, I'm guessing they are used, because to my knowledge they no longer make W8's. Given that, I would never pay more than half of the MSRP (especially subs) becuase you have no idea what shape they are in. And no looking at 'em won't tell you squat, I'm speaking of the spider, voicecoil, backplate....all the things that heat up and eventually wear out. These were origionally very expensive speakers, so $250.00 would be a good deal for the pair and the box.