Probably the SB class for the sealed tight bass. I don't necessarily need something powerful as I want to keep the overall frequencies balanced, the kh120s are doing a good job of all other frequencies.
Thanks for bringing up how I will be integrating them as I haven't thought that far. I was just going to plug them in through my DAC via rcas.
Sealed isn't necessarily advantageous when it comes to sound quality. in fact, it will incur a lot more nonlinear distortion in lower frequencies. It's also worth keeping in mind that the latency in sound from ported subs occurs only around their port tuning frequencies which tend to be a narrow band. So long as that band is in very low frequency, and group delay generated by the port is inaudible. It's well worth the trade-off for lower nonlinear distortion.
The F12g seems intriguing with the paper cones. Is the significance of the sound of the cone material just preference?
The cone material doesn't have much effect on subwoofer performance, outside of the extra weight of some materials. More weight means a lower Fs but also lower sensitivity. In other words, a heavier cone will play deeper but not as loud. Aluminum cones would be heavier than paper.
With a gun to your head, which one would you pick?
Between the SB-3000, VTF-3, and Rythmik F12, that would be an easy choice: the VTF-3. It's a ported sub, and will have far more clean output in the low end. If it was a choice between the PB-3000 and VTF-3, I might have to go with the PB-3000. But at the PB-3000's price, you can also consider the Hsu VTF-TN1 and Monoprice M15 V2. If you wanted to experiment with extreme deep bass frequencies, the VTF-TN1 is the one to get since it can have a 15Hz port tune. The Monoprice M15 V2 is an extremely low distortion sub with unusually low group delay for a ported sub, but it is very large and heavy. The PB-3000; main advantage is the onboard ability to EQ the sub, however, that can also be done with external EQs, and you probably have that ability in your sound interface if it is a good one.
If you aren't concerned about deep bass, then sealed subs enter the discussion again. The SB-3000 is a great one for its size, but also look at the Hsu ULS-15 mk2. The Rythmik is likely a great sub for its size, but it is hampered by its cone area. The Hsu and SVS are likely to stay clean at much louder levels. The Hsu probably has the most output, but the SVS has onboard EQ functionality. There is also the Arendal 1961 1S in this segment which is a decent sub that has onboard EQ and XLR inputs.
