i ran 2 1000s and ill take 3 600s over the 2 1000s any day of the week. keep in mind that you get more distribution of light and can place the 600s far closer to the plant than a 1000w bulb, thus more lumens to your plant.hers the lumens for a 1000, 1 foot from bulb is 140,000 2 feet away is 35,000 3 feet away is 15,555 and 4 feet is 9999. the 600 is, 1 foot away 90,000 lumens 2 feet away 22,500 3 feet away 9,999 and 4 feet away is 6428. now keep in mind that most people who run 1000s keep the lights 2 to 3 feet above the colas. i can place my 600s as close as 6 inches and still see temps below 85. i prefer to keep the lights about 10 to 12 inches from the colas. so for example, a friend of mine runs 2 1000s and keeps his lights about 3 feet from the tops, so his plants recieve approx 15,555 lumens. i keep mine 10 to 12 inches from the tops so my plants receive far more lumens ,approx 90,000. to each their own. do what works for ya.