400w HPS ?

well my grow room is fairly large, about 10ft x 10ft with 8 foot ceilings. will a 400w hps lamp be enough for 4-5 plants to grow or would 600w be better? keep in mind the plants have a LOT of space to grow

400 watt will di 4x4 600 watt does I think 6x6 you probably need 1000 watt for a 10x10..400 is def too small

With that area you can pick out any light you want from 400 to 1000. Obviously the brighter the better, even if you are growing only 1 plant. You'll be fine with 400 watt HPS for 4 - 5 plants, if that is what you are looking to do then go ahead you will grow nice plants with that light. You can expand later on if you wish or just keep your grow the same size. Also you can go to home depot and Lowes to pick up 400 watt bulbs, with 600 you are going to have to order them over the net or pay top dollar from an electrical supplier in your area.

I'd say go with the 400 for now and on your next grow if you want move up to 1000 watt.

If you're room is cooled and ventilated, I would get a 600W "Vertizontal" reflector from sunlight supply.