Hey, on average you should have somewhere around 35-45 watts/sq ft... 1 m = 3.28 ft. I'd go 400 watt in a 3x3, 600 watt in a 4x4, or a 1000 watt in a 5x5
A 1000 watter in your small dimensions of your grow area is overboard. You would run into uneccesary higher electricity bills not to mention dificulty keeping that small space cool not unless you run a air conditioning unit. For that space a 250 watt or 400 watt would be ideal.