1. Go to the store, sit in the chair, and buy the one that feels comfy but won' break your budget. Other than that don't worry about it.
2. From my past experience in the web 1.0 era I've found that startups that focus on furniture over their own product don't do well in the long run.
3. The real thing you want is a HUGE whiteboard.
When I started working from home, I did exactly this and sat in two dozen different chairs. I settled on this one http://www.bestofficefurnituredeal.com/Eurotech-Mid-Back-Erg... and never had a sore back from it in the 2 1/2 years I sat in it.
Now that I'm back in an office, I sit in a Steelcase Leap and have enjoyed this chair, too.
Just don't randomly pick one based on reviews, try them out. Even check to see if your local office furniture will let you take one home for a test drive.
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