I have a HD800 re-cabled with 2x3pin cable on my WA22.
I really enjoy the performance with this combination, though I know it doesn't matter to choose 2x3pin, 4pin, or 6.3mm output on WA22 due to its design.
However, there's still a lot of "true balanced" headphone amps which has XLR output for the headphones.
Here comes the question:
Even the most expensive speaker system doesn't use XLR cables to connect amplifier and the speakers, so why do we use XLR cable on our headphones?