After much reading and searching of forums I think a 600watt hps would be overkill for a grow room that size, so I will go with the 400 watt hps for flowering and the same fan for exhaust (can always run it a bit slower) , the plant is loving the small veg box with two 85watt cfl's and a air purifier, she's really taking off, hope to clone soon, will post some pics.