in an 8' by 8' grow room, if your going to use all of that space, id get a 1000hps not a 400, 400's are only meant to cover 1m squared. If you got a 1000watt light you could fill the room with plants. But a 400 for 8'x8', thats not nearly enough. seing as though you said you dont have much money, i think you should find a smaller space. Im also a bit confused, youve gone from 2-4 plants to 10 minimum, what changed your attitude?