Let's not derail with this music vs HT BS, please.
It is MYTH in the world of modern Subs and it needs to die.
The problem with the speedwoofer is that it is limited in extension...
THAT is what it is "missing."
Now, two 10s might make a 12, but sure as fcuk won't make two twelves. I am a firm believer in multiple subs for whatever purpose. I also am a firm believer in buying for headroom. This is why I recommended buying 2 12's. You get the benefit of smoothing your bass response and making sure that almost anything you throw at them will be reproduced cleanly.
In the case of the Monolith 12s being out of stock, either wait for them or not. That's up to OP.
I would add that the THX Ultra certification is a more stringent set of controls and the 12s will perform better than the 10s in the most demanding of situations in terms of clean and linear output.
The Outlaw Subs, designed by Claridy, are excellent products. I own two X-13s, the X-12s bigger brother. Downfiring is no different than front firing in terms of real world performance. Proximity to the floor does not alter the sound.
BTW, Claridy Audio also designed the Monoliths.
I'm not going to get into Tekton more than to say that how Eric conducts his business is entirely up to him. If he decides to start sending his gear out for third party testing and shows us they are as good as his marketing claims, cool. Until then, I won't buy.
BTW, What really happened between Tekton and New Record Day? That was a serious brouhaha, and now the videos aren't available, none of them! *shrugs