Bright enough for what? The standard package, as I recall, comes with either a fluorescent bulb, around 10-15 watts, or an incandescent, less than 10 watts. Either system would be fine for some of the lower light plants like java, anubias and some crypts, but won't work for higher light plants. Either will be fine for an unplanted tank, where the lighting is mostly for your viewing pleasure.
For higher lighting, there are a few better bulbs available, but to get much more, you really have to upgrade. The ballast will only power up to a specific wattage of bulb, and putting in a higher wattage bulb won't give you more light.