BIGGUY4x4Thank you for your response.
I wonder whether to add to the version for $ 300 or stay with it.
I have Audio-Technica ATH-W1000Z headphones.
I listen to classical and electronic music, e.g. trans.
BIGGUY4x4Single-ended (at 32 ohms+) this has more power than the 789, so for SE only use this is probably the better value. One caveat would be sub 32-ohm planar or other low sensitivity headphones as this appears to run into some current limiting at 16 ohms.