Have a grow box set up already that is 5'L X 3'W X 5-1/2'H , CURRENTLY HAVE FLOURECENTS BUT JUST NOT ENOUGH LIGHT!!!! Too slow! Looking to purchase a digital switchable HPS... Cant decide wether to go 400 or 600 Watt????? Will heat be a big issue in this size space? i have 2 100 cfm fans currently moving air and a stationary inside to move air. I can vent the hood additionally if needed.... I live in southern ohio and my box is in my barn...Does anyone grow outdoors and will the lights combat the occasional 20 degree nights or is winter growing out of the question??? Obviously temp will be an issue in the summer and i am not crazy about using an a/c so trying to decide on 400 or 600...Any Advice