Ideas on how to vent this growbox

hey guys im building a new grow box which will be from plywood and is 24x24x48. i have a 400w hps bulb that is in a bake-a-round cool tube that will be hanging inside the box i was thinking of having one of the sides of the cool tube open which will draw air from the box and exaust through the tube by an inline fan that is covered by a carbon filter that will be attached to the other side of the tube and will be venting the air out of the box over the bulb (to cool it) into a duct that will lead to the outside. the inline fan is 250 cfm (so it says but who knows) will 250cfm be enough to cool the box and the bulb? and take the smell out the air?

?? what if the size of the box was 30x30x48 would that fan be enough?

what kind of fan, in-line duct fan, or the vortex variety?

if it's the in-line duct fan, they aren't good at moving stagnant air, although that's a small grow box, so maybe..

i'm in the same boat as far as venting, it was suggested to me to try a stanley blower conversion, it's as effective as a vortex at half the cost, google it!

The box ends up being only 25 cuft so even if it isn't real efficient it still will move plenty of air I would think. I have a box I'm making and its about 2'x2'x5'. I can't afford a vortex fan right now so I'm expirimenting. I bought a honeywell turbo high power fan for $1 on ebay. It claims in the specs that it moves 220cfm. If I make an adapter for some short 4" duct and run it into the box it may be enough for me. If not, then I'll invest in a inline.