You get by with 4 sf 1000, in 4x4 tent, meaning I should consider having more for 4x8, but I have an ac installed on a wooden stand that takes 2 feet, and 2 of my plants started to die, because of the direct cold air intake, in my last grow, I had to place a piece of heavy plastic on ac and lower down fans direction   because the mixture of cold air and hot air from hids were creating humidity near bulb And bulbs were kinda leaking glass, so I guess I m left with 4x6 to focus on, which normally 800 watt new leds are recommending using in 5x5, and this might do a better job than hids, because overall I required 2000 watt of hids for my tent size , and due to failure of ballast , I had only one working and additional 2 flood led were no good at all, so maybe I m able to fly this ,  I am not a great pilot but I have flown before some old jets, what do you reckon 2 500 , or 1 1000, or as one another said, 2 se 7000