I only run a 400w but I went with a 6" 450cfm can fan. When I compared the 4" fan from htg to the 6", the 4" had half the cfm and used almost the same power and the price was only like 25 $ more. So the choice was obvious, get a bigger fan than what you need and buy a variable fan switch, that way you have a very simple efficient way to adjust temps, and airflow.