Any tube subwoofers out there?

I imagine this is about amplifiers? Power is the answer. If you could have a very efficient subwoofer, the 45 tube has excellent bass.

The NOLA Thunderbolt sub uses an A/B amplifier. I haven't heard it, but it's received excellent reviews from both reviewers and users. It's not tubed, but is considered more of an audiophile subwoofer than most.

You don't see any tube subs because it is such a bad idea. Tubes can't control bass very well, tubes can't drive low impedences well and there is a loss of bass when you go through a mile of output transformer wire. And there would be lots of microphonics from the tubes shaking.

Why not buy a good passive sub and power it with a tube monoblock or single channel of a stereo tube amp?

You can use bass guitar amp instead.