MTX subs are overdesigned and underengineered in my opinion.
Subs which are better (subjectively):
Adire Audio Brahma
Image Dynamics IDMAX
Resonant Engineering RE XXX
Treo
Incriminator Audio
Digital Designs
Although Im sure a head-to-head comparison would be more accurate, they still would reveal that the subs from these companies (that can be had for much less $$$$ - which is always an advantage) perform at least as good if not much better.