Do you have an example of your airflow in the 800D? I've run the 800D, HAF X, and HAF 932 in my personal setups and found all to have their own unique strengths, but the 800D surely didn't have 'great' airflow. It's a great space to work in though.I have OWNED the 800D and with proper fans in this case it makes for GREAT airflow.
Its a very versatile case
Uh.. I'll say the one thing the Haf has over the 800D is better cable management especially behind the motherboard tray.Out of the two cases I would go with the HAF just cause I love the hard drive bays better, but the 800D does have cable management over the HAF which is a big factor in buying a new case.