And as far as a pound on 4 plants. Unless you are planning on vegging those things for 3 months, i dont think your gonna come close to a pound on your first grow using a 600 watt hps with only 4 plants. I veg for between 3-4 weeks under a 6 bulb 4 foot t5, then switch to 2 1000 watt hps (only running one right now), and I get around an ounce per plant. Occasionally when I let them veg for longer(2-3 months), or throw a mother into flower, I will get a QP from a plant in a 5 gallon container, but rarely will I veg them that long. I make up for it by adding more plants. And with each 1000 watt hps, I only pull about a pound-a pound and a half every month and a half or so.