I spent the last 3 weeks researching chairs.
Here's a good link. Topic is programmers and chairs but same idea.
Investing in a quality chair
Some of the top choices,
Herman Miller Aeron
Herman Miller Mirra
HumanScale Freedom
Knoll Chadwick
Raynor ErgoHuman
Steelcase Leap V2
I ruled out Aerons since I've used them in the past at work. Just wanted something different. But there are a ton of them available used on Craigslist. Make sure you get the correct size (A - smallest, B - most people, C - largest)
I checked out a Mirra from someone on CL. Thought it was ok but this was the basic version without the adjustable arms or lumbar. Could have bought it for $250. Decided to pass.
Guy had Knoll Chadwick for $250 on CL. I bought it because he lowered price to $175 but regretted the decision. Arms were not adjustable and not much back support. I realized I need a high-back chair. I'm 6'2". But I was able to sell it for $250 on CL. +1 for buying brand name.
Another guy had the HumanScale Freedom on CL. I was able to buy it for $360. New, they go for close to $1k. Very nice chair, headrest is a plus. Principle of chair is simplicity, very few knobs. Negative for me, the headrest doesn't cradle your head when sitting upright, only when you lean back. Arms are ok but not very big. I like to slump back and have good arm support.
I've seen a lot of (Youtube) reviews on the ErgoHuman. It's available online at Office Depot. I don't see it being sold used so there doesn't seem to be a big aftermarket. From what I read it's made for taller people. Videos seems to suggest the headrest will cradle the head better. Armrest can be set pretty high. It's available in some places for $607 new. There is a newer version that goes for $745. Model number is V200HRBLK. They may have improved durability since it's one of the complaints for the first one. I'm gonna see if I can sit in one, if really feels that good, may sell the Freedom and go with the ErgoHuman.
Heard lots of good things about Steelcase Leap V2 but haven't sat in one yet. No headrest. Probably not gonna go this route. Either keep the Freedom or get the ErgoHuman. 2 places where you can try out some of the chairs, Design Within Reach and Room and Board.
Hope my experience helps.