It doesn't even really have a ton headroom because the e series will handle 750w no problem. And to be truthful there are a lot of factors that will make it where you actually getting a little less wattage from the amp. Things like box rise and most likely a little less voltage than the amp was rated at. I would pair the e series up with a 750w amp, and I would pair an sa with a 1000-12000w amp. That being said, there is nothing wrong with running an sa on a bit lower than rated power. It will still sound great and maybe a bit better than the e series. But they are both good great subs.
That site is b-stock. I've actually used them a few times and it's hard to tell what is b-stock about the subs. The last pair of e-8s I bought had some excess surround glue, but I had to take the mounting gasket off to even notice. There are no performance issues just slight cosmetic things that are usually not noticeable
