I purchased a Horn Sewing chair about 2years ago. I am plus sized and I could tell the cheaper office chairs would not last or give me the support I need over time. I spent about $300 and feel like it was money well spent. The chair is very comfortable.
I took a class earlier this year at my LQS and she had several sizes of the heavenly chair. I really liked the one I used and wished I had known about them before I got my chair. Oh well......
maybe you can find a dealer to go look at them. Good luck!