I don't think the math for lights is so cut & dry. You don't have a pile of 24,000 lumens that you sort up and divy between your plants. Each light has an area that it illuminates, and the effect is cumulative. What I mean is that, depending upon where a bud site is located, it could be recieving lumens from three primary cfls - one may be 1" away and be contributing 1800 lumens, the second could be 5" and give 1200, the third 3" with 1450 lumens to contribute - making 4450 lumens (these numbers are totally from out my a$$
). But now consider the effect of secondary bulbs - basically any point of light with an unobstructed line to that bud site. The addition of reflective walls and hood also add to the amount of light available. With 12 CFL's, you could attach them all to a flat piece of wood (first painting white or covering with reflective material) in a pattern that looks even and make a killer sea of green hood (I found that CFL's yield best in a s.o.g.). I did well enough with 12 plants and 3 desk lamps (each split with a Y and outfitted with a blueish 26w and a reddish 42w). No matter what, I'm sure you'll have fun.
E4A2S