AH man it sucks that noone has replied to your question , but I'm currently growing a single plant under a 600w and I can tell you that Ive previously grown more than one plant at a time but after growing this one I might just keep growing single plants under the 600w. The plant is HUGE and is taking up all the space in my grow tent (homebox L) at 3 weeks flowering it is already bigger than my Master Kush was when it was harvested and I pulled about 6 OZ off the Master Kush so I'm shooting for NO LESS than a 1/2 LB with this current plant. Oh yeah the plant im growing now is Gforce, its a Nothern light/skunk cross. But if ur gonna try a single plant under the 600W then I say go for it because i'm not disappointed with my results so far