I have two Kube 10b subs.
On the website it says the subs use DSP to make the bass accurate.
It's not a bad thing - the design was purposeful - sealed design was chosen for more accurate bass (although 3dB less of it compared to a ported design). Small sealed boxes driven naturally (sans DSP) need very heavy cones and very very high high power amplifiers and handling. Or they need light cones and high-ish power.
Without DSP, for flat frequency response down to 24Hz in that box, the just the cone of the driver itself would probably need to weigh 5lbs, and you'd likely need a multi-thousand watt amp to drive it. But in this situation, the voice coil would overheat. No matter how good the speaker, thousands of watts pumped into one cubic foot = hot beyond belief in no time! So now we know that due to physics, a sealed speaker this size with a flat frequency response is an impossibility. Fortunately DSP is pretty awesome.
At this point, the "Q" of the speaker (speaker system - the speaker in the box as a unit) is on the high side. This means the spectrum around its resonance frequency has a peak in the frequency response - the middle is probably up 4-5dB, likely somewhere between 90 and 110Hz. The DSP is used to equalize this out. There's also some ringing at this peak - DSP fixes things again.
The mods to the audio signal are not perfect, but with DSP done really well, the result is sound that's almost as good as the box being 3ft x 4ft x 4ft (like it'd be naturally for your desired response), while the box is just 1ft x 1ft x 1ft !!!
There's one more caveat to small sealed box design.
But first: a benefit: your woofer gets to get less power around its resonance - DSP lowers the signal at and around the speaker's resonance frequency because it's not needed (the peak
The caveat: At really low frequencies (lower than resonance), when the driver is moving, in addition to the force placed on all woofers by the air they move to make sound, there's added resistance from the box (a lot of added resistance). The space behind the driver is very very small - just a cubic foot or so of air is there, and when that 10" subwoofer moves in and out 1" (which I believe is about its maximum excursion, maybe slightly less), you're needing to compress 1700 cubic inches of air by over 100 cubic inches! Then you need to stretch it by 100 cubic inches!
60Hz? You're doing that 60 times per second!
It ends up being a lot more work than if you just had the speaker in free air - this is why the subwoofer comes with a quality 300W RMS amplifier. If the speaker was just in open air, the pressure would equalize, eating all your bass , so good that the box is there. And good that the box isn't big enough to fit half a cow (that's probably how big it's have to be to extend to 24Hz -3dB naturally). Although the sound is good, the size of the box itself would likely ruin the aesthetic of the room and also probably affect the room's acoustics...
I don't think you're going to find a smaller more accurate sub than the Kef Kube 8/10/12b. Dual 10s was the lower limit for me because dual sealed 10s is like a single ported (you lose 3dB). I would've got dual 12b's, but there was a sale and the 12s were gone and the sale was really good and the only difference was +3dB and 3Hz lower extension that I'd be missing so I sprung for the 10s. They're good.
Yeah, basically I said this because all sealed subs smaller than a compact car have DSP to make the enclosure a manageable size. With powerful magnets/motors, Q of manageably sized sealed subs can be kept reasonably low so that DSP is able to effectively extend frequency response, attenuate peaks and minimize ringing to a level that's imperceptible
Good luck with your config