new grow operation......need some advice

have an area of about 12ftx12ft ......i plan to be growing organically with high quality seeds indoors.....i will be running a 1000 watt mh and hps light and a 400 watt mh and hps both with umbrella refletors(2x2 for the 1000 and 4x4 for the 1000) ....i know this will be plenty of light to start off a good 15 plants but what i want to know is when the plants are about 5-6ft tall what would be the right amount of plants to have under these lights. My guess is i could put about 8-9 under the 1000 and 4 under the 400 but that would be giving the plants more than 15,000 lumens per plant. is this fine or do i need more or less plants????

Well, it all depends on how bushy the plants are. The only problem with growing plants that large indoors , is that even with a 1000w it's pretty hard to penetrate the canopy of the plant. Have you thought about using the SoG method?

a 5-6 foot plant with only one light is un realistic indoors...yeah it can be done but you are way better off with smaller plants...less time in veg, you have to figure that the light can only penetrate maybe 3 feet of growth at the most but if say you were running multiple lights then you could grow bigger plants because they will get light from many angles, consider a light mover also