If your chair is pretty good already, and you don't really want to spend so much on a new chair, you might try going to one of those "back stores" and getting a lumbar support. I've got a Mckenzie superRoll. This gizmo attaches to your chair with an elastic strap. It takes a little while to get used to it, but now I wouldn't trade without it. Might be worth trying for $20-30 before you spend $200-$3000.