Woo Audio
Jack Woo has a comprehensive line of eleven tube headphone amplifiers ranging in price from the $495 WooAudio 3 single-ended OTL using a 6922 driving a 6080 output tube, to their new $10,000 (estimated) flagship WA-234 mono-block amps. These impressive mono-blocks use a unique "key" that that is inserted into a tube socket, and provides the circuit reconfiguration needed to allow the amp to use 2A3, 300B, or 45 power tubes. I'd love to hear the new Audez'e LCD-3 with these amps.

Jack was also demoing the fabulous Stax SR-009 ($5200, available from Woo Audio), which I recently reviewed in a high-end headphone shoot-out. Man, the Stax are great headphones, and they sounded very well driven by the WES ($4990) tube electrostatic headphone amp, which uses the EL34, 6SL7, and 5AR4/5U4GB rectifier tubes.

All Woo products are manufactured in New York.