Some say the rule of thumb is 50w / 5000 lumen per square foot of growing space as a medium expectation, the more the better
The least you can get away with is 30w / 2500 lumen per square foot so they say !
You may wish to take a peek at dual spectrum cfls 125w, 200w, 250w or 300w or just a combination of blue 6500k & red 2700k single domestic cfls bulbs some of these you can find in your local hardware store you may have to search a little for the blues tho.
Hope that helps.
"Mama always said growing was like a box of chocolates. You never know what you're gonna get."