you're going to require proper venting. Look for proper blower fans (120cfm - 440cfm) and then possibly and intake fan of equal or near outtake. They will run you a decent penny but its really the only true way, axial fans will _not_ work, they can't overcome static pressure.
a 400watt gets...
cheap products, they only have 1 digital ballast, what gives? Also the shipping is a little high.
often times you can go down to local grow shop and they'll hook you up.