enough ventilation for box?

I am building a grow box that will be 4'x4'x6'. It will have a 400w hps and 3 65w cfls. I have a 6" 250 cfm vent booster fan for exhaust which will be near the top and a regular 8" fan near the bottom for intake.
Do you think this will be adequate to keep the box cool enough?

the biggest thing to help with heat if your worried about it is get an air coolable hood and attach the inline fan straight to it and vent it out of the room your growing in or theres no point in exhausting it ya know. and with a fresh air intake you should be fine bro. 250cfm might be alright but maybe upgrade to a 6inch vortex inline fan if your pocket can afford it man its like 170 on ebay with free shipping. that will keep it cool enough i think. if oyu also have the loot man jsut get a grow tent to save on all that work if oyur not looking forward to building the thing ya know.