info on halogen lights.
I have a 250 in ~25 cubic feet.. and was trying to cool that with a 55 cfm muffin fan.. ambient temps were ~75 and in the cab would peak at around 98 sometimes... i ended up getting a 4 inch vortex and at 172 cfm and with that much cfm in my space there is really no chance for heat to build up.. but ambient temps in my spot dictate how well my cabinet stays cool... if your growing in a warm spot and are pulling in hot air... well it is what it is..
Here is some more information on lighting coverage.