I know this is old, but I cant believe the info people are giving at this forum, do the ******* math.
1000w HPS - 145,000 Lumens
600w HPS - 92,000 Lumens
400w HPS - 58,000 Lumens
600w HPS + 400w = 150,000 Lumens
More Lumens with a 600 and 400, this is because 600w HPS is the MOST EFFICENT HPS wattage light. Sooo, two 600 watters is most output for your money, price and electrcity wise, plus less heat than 1 1000w.
However in this case, running a 400w and 600w will cost more moneys, since a 400 really pulls 430 and a 600 around 640, so your pulling 1070 watts for 5,000 more lumens as oppesed to 1030 watss for 145,000.. BUT youll be reducing heat by nearly half, and addding in the watts used for your inline fan to cool a 1000w and your gonna spend more in the long run with a 1000 watter...