small out building

hiya lads
i have a small outbuilding that i am currently growing with a nft tank size 158cms x 53cms they are growing ok i currenlty have 3 plants in that and the mother is now flowering in a large pot next to it,
when it has finished i want to expand a touch, i am currently using a 400w light but would like to know whats the best set up to use all of this room?
the room size is 3.6m x 1.2 m ? and how many plants do you think i should be browing in ther at teh mo i dont haev any kind of exaust system in there for these 4 plants only a small osc fan

To use the whole room you want either 3x600W or 2x1000W lights, personally I'd go with the 600's for better spread of light and the extra lumen per Watt.

The number of plants depends on what type of grow you want and whether your growing from seeds or clones, but anywhere from 20-200 I reckon.

thanks mate what about an exaust ststem though?? cos it gonna get hot in there i imagine
daz