Best MUSICAL subwoofer for Maxx 2's quality sound?

I posted this under the "speakers" forum, rather than "home theater" for a reason.

Looking to either buy another M&K MX 5000 subwoofer to go stereo pair setup....or, maybe a whole different subwoofer setup.

Running Wilson Audio Maxx 2's, and want to supplement the very low end (below 80 Hz) musically and very powerfully. (Maxx 2's are powered by 2 McIntosh 1201 monoblocks).

Suggestions? Just add another MX 5000, or change? If so, to what?

Thanks, in advance.

John