Dual vs single sub

Stereo bass? Vinyl mixes bass to a single channel for practical reasons. Moreover, localization of low bass is a non issue as you can't really tell where its coming from, only the higher harmonics is a clue, AND most music only have one bass instrument.
More subs is for other reasons, but stereophony it is not.

While most of this is true, the comment about vinyl is not. We don't mix bass at all when mastering. That is a technique used to reduce the time and cost of mastering time but its not something cast in concrete.

The idea of 4 subs is the correct one. In case its not clear, the problem is standing waves and this is not easily corrected by room treatment if it can be treated at all.

But its easy to treat with 4 subs. Just do what Duke mentions above. He's a modest individual and didn't mention that he makes some of the best subs out there- the Swarm, which comes in sets of 4. Two of them are placed asymmetrically in the room and it is this placement that breaks up standing waves, allowing you to hear all the bass notes at the listening chair.