If you measure directly in front of the cone, you'll notice it outputs a smooth response.
Pretty much every peak and null in the chart is room-caused.
We generally don't need to measure above 2-300hz, and then smoothing can be turned off.
I have like 32 subs in 3000cuft, so for 10,000cuft the sky is the limit...
12inch cubes up front won't be enough. The PA 12's have significantly lower efficiency and power-handling and cone-area.
It is what it is though, still better than not having any I guess.
I prefer my mid-bass to come from the front of the room, but some don't mind it nearfield. Putting them nearfield will require that you add delay to them. The furthest speaker has no delay, and all the other speakers have delay at a 1.1ms/ft rate from that reference point.
AVR's calculate it for you, but generally only for 1 sub so you'll have to turn it off, which will then be a problem for the SVS unless it has onboard DSP with delay.
As for mixing sealed and ported, ported subs cause a phase-shift near and below tuning. Sealed subs don't, so as long as the sealed subs are HPF'ed comparable to the ported subs, then the phase-shift should be insignificant.
Where you might have a problem is using ported subs for mid-bass, that will cause a shift at say 40hz, which is less than ideal.
Conversely, if you try to use the sealed subs for 1-20hz that will interfere with the subs ported to 15-20hz.
Using all-sealed is never a problem, using a bunch of ported subs and mains is the problem. (There is no free lunch.)
Hence why my system is pretty much an all-sealed design, yeah it's not efficient in the 13-20hz region, but it's the highest-density, smallest and simplest design, mostly headache-free.
The SI-24's do really well when sealed because they have lots of cone-area and excursion to make up for the lack of the extra SPL generated by the port near tuning; so people have done fairly well using multiples of those for the space occupied.
A subwoofer box the entire length of the sofa with sealed UM-18's on all 6 sides (raised up with small legs), say 10 18's and 10kW... should be good-start. hehe!
If that's too expensive then maybe 10 PA-460 with a bulk discount and 5kW.
This formula is way oversimplified but SPL is basically:
cone-area x excursion x cone-efficiency x power-handling + any port displacement at tuning. Minus the distance-law.
That's why all of the boxes with multiple large cones have done so well on data-bass (MAUL etc), as have the larger coned subs (SI-24 etc).
Porting and Horning the boxes help too, but that has some disadvantages with mixing box-types.
The best way to "get loud" is with cone-area because it doesn't add heat or distortion.
The next-best way is with excursion, which requires power, which means heats + distortion.
It's not linear either, 2x the power is like 4x the heat and 40% more excursion, and an untold amount of extra distortion.
Excursion, power and heat are your enemies.
Cone-area and coil-area are your friends.
Obviously some amount of excursion and power will always be required.
It takes about ~32watts to push 32 18's to 1mm, and it takes about ~3200watts to push 1 18 to 32mm's; and both are the same SPL!
The single 18 farting and melting in seconds/minutes, and the large array is bass-for-days with zero distortion.
and then what happens when the 32 18's goes to 10mm's? EXACTLY!