Check your math again. Those two 18s might put out ~2000 lumens. Here are some very small basics for CFL:
* At least 100w (real) for first plant, and 50w per each additional. That is the bare minimum, more is better.
* CFLs don't throw their light far, so distance should be no further than 2-4" from more mature plants. 4" is good for young plants, maybe as far as 6" on newly sprouted seedlings.