I run an aircooled 430W Son Agro in a pretty small space. (2' x 2.5 ' x 7' -- and the 7' could get smaller w/u much impact.) I put four to six under it and am generally happy. Yields are very erratic for me as I'm a fan of Bagseed Surprise but the setup is fine.

Go to a 400 and a couple blower fans--one for the hood and one for the space--if you can. I would only use a 150W in very small cabinet or PC case setups, or to veg a single mother plant in her own cupboard, or something like that.