Is More Better?

You might find some of the this helpful.

https://www.harman.com/documents/multsubs_0.pdf

https://www.youtube.com/watch?v=RE6g2IawzSQ

Unless you’re setup is in an aircraft hanger, that’s crazy overkill, but you do you.

This too-clever-by-half comment is not that clever. It reflects a misunderstanding of why multiple subs are helpful. It’s about the room’s acoustics. It depends a lot on the room (see comment in next paragraph about measuring). 

Having three subwoofers isn’t about more bass, but achieving a more articulate and even bass response throughout your room. A single subwoofer creates "hot spots" and "nulls," leading to muddy or boomy or weak bass. Multiple, strategically placed subwoofers smooth out these peaks and dips, providing tight, detailed, and clear bass across a wider listening area. You should be prepared to put them where the sound is best, not where they "look good." The goal is audio balance not visual symmetry or prettiness.

You will need to learn a little. Measurement and Digital Signal Processing (DSP) are essential. Using a microphone (UMik) and software (REW, for example) can help measure your room to reveal problem areas. DSP then allows precise equalization and time alignment for each subwoofer, ensuring they work harmoniously. 

I recommend Rythmik sealed subs as better options than REL, e.g. They are more flexible (adjustable phase, for one) and more economical.

is more subs better?

The answer is “yes, but….”

For 2 channel audio, Smoother Frequency Response: Multiple subwoofers can help to even out the bass response across the listening area, reducing peaks and nulls (dead spots) that are common with a single subwoofer.  The second subwoofer makes a huge difference, but each subwoofer added afterwards yields increasingly smaller benefits.

So yes, each added subwoofer benefits a smoother frequency response, “but” is adding 2 more subwoofers better than spending the funds somewhere else for greater sonic benefit…..?

Check out AudioKinesis and the 4 subwoofer swarm ... the extra subs are very much about getting even bass response throughout the room ...and setup is not difficult with 4 subs - a single sub is most difficult to place...

Uhm what will be a better purchase than a subwoofer to combat room mode stacking and helping fill some nulls of the initial sub system?

Cos nothing bought outside of some broadband absorption is going to be more important than bass management via a multi sub system in giving your system a greater sonic benefit and that's physics. Can't run around that with voodoo purchases