What are important features in a listening chair

Another vote for Eames plus ottoman.

Better pay $5k for a chair than for a cartridge or power cord, I guess.
Not for me, though, I am on the floor too, and anyway, if the music is good it doesn't matter much unless you listen for hours straight which I don't.

Health. Movement. You (not the chair).

Since the focus (so far) has primarily been on comfort and sound quality....

Studies are now showing that standing (at an upright desk) is not much different in impact versus sitting. 

An old school and simple wooden chair that allows for an upright posture. Practice bracing of the abdominals and lower back muscles.

Too late. I've got a permanent slouch.

At 64 years old I like one of those motorized lift chairs. When getting up to use the bathroom I don't have to fight the sound pressure coming from the speakers that keep me plastered against the back of the chair.
LOL