The right chair will definitely help. The few times I worked from coffeeshops for a whole day, or at the kitchen table with a regular chair, my back was killing me by the end of the day. When I got a 2nd-hand Herman Miller Mirrah the improvement was massive and noticeable in a very short amount of time. When I moved to the current Aeron I didn't notice any difference right away but in the last year I started feeling crap again.