Mixing subs, ported +sealed, or 2 different ported... requires a lot of skill and expertise to make work.
If you mix subs with two different levels of output, the more powerful sub will be limited by the less powerful.
You have been given excellent advice and are continuing to fight against it.
You have a challenging room set up, with more sofa than anything. You have a large room volume.
One sub, properly set up, might make your LP sound good. True. But anybody else in the room may very well be left wanting for any bass at all.
(I have, from my experience doing the sub crawl, a known spot where all LF disappears. Now, since you have set such stringent requirements over what will and will not work for you, you may very well end up with crappy bass anywhere that matters with this approach. You cannot overpower the laws of physics with even the most powerful of subs when using just one!)
At this point, frankly, I do not know how to offer any further help!
If you take the sub you have now, and do the subwoofer crawl, you can identify places in your listening area and larger overall room that may contribute to better bass performance across your seating area. If you choose not to do this and learn how bass frequencies perform in your room, you are selling yourself short. Switching to a single sub will not help matters, especially considering the limitations you keep putting on the options, and even if the sub is 20 times more powerful. You cannot cheat the physics behind this.
If you decide to have an honest conversation about this, cool. Right now, you are asking for smaller subs and better performance, and you seem completely uninterested in actually learning how to work with the Acoustic Properties of the space you have.
Peace.
I'm out.