Of the choices, 400 watt. However, maybe a 400 HPS with a 250 MH (for the UV rays) would do. I like the 600 HPS with 400 MH for my own, slightly larger area and I keep the ballasts out of the grow room to fight heat buildup.
High Voltage Reviewed by High Voltage on . How Much Wattage Should I Push? Growroom Size- 6 Feet High 3 Feet Wide 1 1/2 Feet Deep. Looking whether to put a 250, 400 or 1000watt HPS system in with a 50cfm fan installed without reaching critical heat buildup. Suggestions? Rating: 5