I allow a minimum of 2 sq. ft. of floor space, per plant, and as tall as physically possible ... my cabinets are around 7 ft. tall, and wish I had more (remember, you lose at least a foot, due to the container height, plus a couple feet more, due to required distance from your plants) ... 50 watts per sq.ft. is advised ... you can veg your plants quite well with the HPS (high-pressure sodium) lamp, you use for flowering, too ... I personally don't see much difference, when using my metal halide, for vegging ... with 4 plants, in the required space, I'd recommend a 400-watt lamp ... you will NEED lots of ventilation, and temperature controls, too ... be sure to leave room for an oscillating fan, too ... good luck :thumbsup: