Need Help Choosing Light For 4x4 Tent!!!

I want to make a veg tent with a 4x4 tent, I will have 12 plants in there. I will veg for 30 days in 3 gallon pots than into the bloom room. I will use air cooled hood and a inline fan and filter,what light would y'all recommend a 400 or 600 watt light? I am mostly concerned about keeping it cool not quite sure where to vent the hot air.

Your ability to cool the heat produced is the deciding factor for what size light you should use. Generally a 600 or 1k is ideal for that area, but you need to figure out your cooling situation.

600 watt halide with a sunlight supply blazer 6" air cooled hood.

I'm leaning towards the 600 myself as I'd like to do a perpetual and I'd have to do half the flowering in the tent for it to work. Could I just vent the exhaust outside and the passive intake would pull cold air off the floor to keep the tent cool?? My house stays bout 58 all the time till its summer and than about 70

400w is too small for that many plants in that size of container. 600 or 1000 will give you bigger foot print. You will need a closed fixture with in-line exhaust fan to keep the temps down.