Buy it on: Amazon
Of course, if you are willing to shell out a grand, you can have revolutionary back support with the Steelcase Gesture Chair. The ergonomics of this chair are amazing for your spine and will correct your posture while you spend countless hours playing your favorite games.
This chair moves and shifts as you do, allowing you to have proper back support in almost any position. The only real problem here is that the lumbar support isn't adjustable.
If you can swing it and want to make sure your back is getting the proper support that it needs, do yourself a favor and pick up a Steelcase Gesture Chair.