wow someone told me, "oh get a 600 watt instead of your 400 cause the lumen output of a 600 is almost double that of a 400. Well...at first glance it does look double...until you do the math. For every 200 watts from a 400 hps = 26,500 lumens. And for every 200 watts from a 600 watt hps=28,666. So...I don't think its worth upgrading, especially since I would have to change the whole exhaust setup if I went with a 600 cooltube. I can still grow bomb stuff with my 400 right? Im thinking about getting mylar. hmm I wonder how I can figure out how much mylar I need for my room.