But cheap is good! Although it looks like the AW831X are no longer made, but have been replaced by the AW831Q. As far as I can tell, they are the same woofer, however. Same specs, same design, just a different letter on the end. And it seems the price went up . . . I commonly see $69.99, the lowest about $45.
I don't see that they are labeled as Free-Air subs, however. Are they are just normal subs that you are using free-air? I was always under the impression that you should use subs that were made to be used without a box, but I don't know much about this stuff anyway.