In the grow critical mass tree, the 600w lamps are naked. Does that work? does it get to hot? what lamps would be right for that? in other words do you need the expensive hort lamp or will any good or decent regular price hps 600 lamp do as well. Remember that the lamp will be naked...

If you use CO2 you want to use a vented hood on your light with air forced from outside the grow room to another outside room or you will exhaust all your CO2. Other then that, it is a matter of how much heat you will get off your light. If your room is too hot, put in an exhaust fan. If you do not run CO2, you are missing a lot of growth, but you do not need to run a dressed light.

Your expenisive hort light probably has a blue and red spectrum light. You are better off with the blue added to the hps lamps like the hortilux.

Hope that helps. Multiple posts only use up space and will not get you answers any quicker, slower if anything cause people don't like double posts.