Where are you getting those from? I believe the 8000 series is an old model but I'm not sure how old. The new model is the 8500, probably no difference but you may want to find out how old those are.
MTX makes some good subs. One of the installers at work has 4 of those build into his rear deck which we turned into a box and they are powered with an old MTX 1000D. It's mind-numbingly loud. lol