I think the MBM is designed for those with very small sattelites that do not play well down to the subs usual range of 80hz and below, as the M22s reach down to 50 hz easily I do not think you will notice a huge improvement for the money spent on one. Now that you have a spare 8" driver I guess you have nothihng to lose but time trying it out.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70