Forget about power, give us your lumens/square footage ratio.

You want to shoot for 5000+ for optimal growing.

For instance, I have two 42 watt cfl's each putting out 2800 lumens. Considering I'm only growing one plant in a roughly square foot area this sufficed. If I just doubled my dimensions to a relatively modest 2x2 foot area I would need 4x the lumens.

The two 2800 lumen bulbs worked fine for vegging when the plant was still relatively short but I bought a couple 13 watt cfl's to hang in the chamber outside of my cool tube with each putting out 900 lumens. This helps illuminate the lower leaves and gives the room a nice boos to over 7000 lumens in the smallest of grow spaces.

Give us that information and then we'll see whats up.