you would do better with a 1000-watter for that 5'x5' area ... your 400-watt lamp is best for a 3'x3' or a 2'x4' area ... also, I have used 400-watt EYE Hortilux lamps $$$, and I now use cheapo lamps that only cost about $10 apiece ... I have observed NO difference between the lamps regarding plant growth, bud density, or lamp life ... I buy my lamps here: Light bulbs, Rope Lights, Halogen and Fluorescent bulb - 1000-Bulbs - The Light Bulb Superstore ... I have always had good service from this Texas company, with quick replacements when I had a couple arrive broken ... :thumbsup: