any tube amps of that pa2v2 style?

You might want to investigate the Little Dot amps. I used to play one of the budget Little Dot amps (now discontinued model) with a portable headphone and I loved it. 

If you want a low output impedance you have to have output transformers. Good ones start around $200 a pair. If you want an OTL with low output impedance, the only commercial offering is the Zana Deux, thanks to the 6C33C output tubes.

You do not want an amp that has an output impedance higher than the impedance of your headphones. A lot of OTL manufacturers will tell you that they will work, but that makes the power delivery funny and you'll have poor bass control.

Your best bet is a solid state amp. Chips have a low output impedance and sound very good despite not being as fashionable as tubes. Solid state costs less because it doesn't need expensive transformers to deliver high voltage or handle output. Inexpensive (but good) power transformers are all they need and solid state requires less casework and assembly, too.

If you really want to save money on a tube amp with output transformers, build your own. You can find several plans over at Headwize. Spring for some nice Electra-Print output transformers and use Hammond or Plitron for power. If you go with non-boutique parts, you could get one together for about $500 in parts. I don't know how to put one together for less, and I don't think anyone else does, either, since there aren't any cheap ones out there. You can get cheap labor in some countries, but the raw materials costs are about the same the world over.