I think you could use data-bass.com's measurements of the Outlaw LFM-1 EX to get a rough idea of how the VTF3 would compare to the XV15. The VTF3 and LFM-1 EX have a lot in common, however the VTF3 has a bit better deep bass performance due to its larger ports. The XV15 has an advantage, but not a big one, and it depends on what mode you run the LFM in. For instance, if you run the LFM in max extension mode, it basically equals the XV15's deep bass performance, but the XV15 has a bit more output from 30 to 50 hz, topping out with a 4 dB lead at 50 hz. If you run the LFM with two ports open, it mostly erases that mid bass advantage, but gives up a lot of 16 hz output. To sum it up, the XV15 can match the LFM's output in either mode. The VTF3 ought to perform similarly, but perhaps with slightly superior deep bass output than either, and given its cone diameter vs port diameter, I would guess it's less at risk of chuffing than either at high volume playback as well.