because of the conversion, a 600W light is the most efficient in terms of Lumens-to-watt, however the increase in the amount of lights will create more even lighting over the canopy, and you can hang them closer since they don't get as hot as the 600W. as far as lighting under the plant canopy, i haven't really experimented with this myself, I usually lollipop plants to increase hormones in terminal buds and shoots by cutting off really low branches and leaves that aren't going to be gettting light anyways...IMO i think that lights under the canopy is going to be a waste of time and energy because you could be using that light for increased growth at the canopy.
i am thinking of getting two 250 watt hps and removing my 6oo watter because of heat and electric costs also i could veg with one only and then both together for flowering it should give more lumen output than the 600 looking at charts for light output and be cheaper on elecy bills anyone agree all comments welcome
also can arrage one light to give more light penetration under canopy of leaves adding to lower bigger buds
