It is recommended that you use a 600 watt for an area 3x3 and a 1000 watt for a 4x4. So in theory you are going to need 2 600s.
You may look into how strong this really will be under the heat. My hood alone weighs in at over 50 lbs, yes its one of the heavier ones, but if you are going to do 2 600's in there its going to have to be air cooled so i wouldn't doubt you will be hanging 100 lbs from the top.