And simply add a different Subwoofer (different in everything, from the size of the driver, the enclosure design, everything!) the manufacture said it will add a bottom end (again no low pass filter inside) and without worrying the group delay and phasing problem?

I got explaination from Mr. Wayne Parham, that there will be a problem, but in small room and with few driver I can't ignore that. But in the case of bass guitar cabinet, even for the stadium size concert?

Is that OK?

Regards,
Gabriel