I wholeheartedly disagree to most of these statements.
The article by Perry Marshall describes an alternative approach to designing ported speakers, it's not a cookbook for "improving" existing designs. While certain aspects surely apply in common, the pros and cons must be evaluated.
I don't share your comments on subwoofer usage at all. From theory and even more from practical experience one single subwoofer (even a very cheap one) can greatly improve real world performance in a typical home,
if high pass filtering is applied to the mains.
@Valdo already owns a WiiM Amp that is capable of this exercise, so a sub is all that is needed.