Just a couple of thoughts....
Hsu is soon (!!) to release the VTF-HO that you may want to consider! (That may be why that VTF-3 is on sale.
) They also are returning to the cylinder design with their TN series.
I think if you're considering a tube, you might want to think about a separate amp with either the SVS or Hsu. Onboard (inboard) amps tend to somewhat spoil the sound design benefits of cylinder subs.
Come again?
No matter which you get....you're gonna have some fun!
Happy hunting.