Hey, thought I would chime in as well. If your keeping one end of your hood open to pull air across the bulb and out of your space then 400cfm should work nicely! I use a 460cfm 6'' ecoplus centrifugal fan to extract the air from my cab over the bulb (400w)then push thru the DIY carbon filter I made.I was trying for a passive air system. The speed control I bought was 23 bucks and I cannot recommend living without one. Starting with a setup like your talking about might save you from having a box or two of misc fans and junk that you later didn't need (I throw nothing away!). I was able to unhook some intake fans because my fan was big enough. I later added another light that wasn't air cooled and it was cheap with the ballast attached so it raised temps but the fan was big enough to regulate the heat. Happy Growing!