I started using an Ergohuman about 3 months ago and am quite pleased. IIRC (and correct me if I'm wrong), the adjustable lumbar support and/or headrest on the Aeron are extra. They come standard on the Ergohuman.

http://ergohuman.com/ergohuman-me7erg.htm

(PS: drewcrawford already linked an Office Depot rebranded version for cheaper, so please up-mod him too if you found this helpful :) http://www.officedepot.com/a/products/690690/Realspace-PRO-9...)