Using a cool tube or sealed unit will decrease heat significantly, allowing more lights in a closed location. I would say 3 600w lights is close to a small bedroom if not a large walk in closet. They also make an amazing product I saw at my local hydro store called the icebox which just snaps onto the end of the vent near the sealed light housing and cools the air to the point it was colder than my home a/c. That might be a route you take since you are working on a much larger and more expensive set-up to begin with.