No I don't think you can really make it too bright, but i've read in a grow guide that around 50watts per sq foot is optimal, but that was talking about HPS so you could probably increase it for cfl to 60 or 70 watts per sq ft,but i've seen plenty of people growing with more than that with no apparent harm to the plants but supposedly the plant can't use much more than that so the light just gets wasted.
When you starting your grow btw?