Just a quick note on warm vs cool..
Most people will put in a mix of the two if they have more than one light. Yes the warm white might be closer to natural light ( I haven't actually looked at the specs on a warm white bulb lately). However the cool white puts out more blue light which is the primary light that plants need for good photosynthesis. Too much red light (warm) and the plants will get tall and spindly but are more likely to flower as red light promotes flowering. Which is why most people will put in a warm tone here and there if they have multiple bulbs. For a single bulb application I would go with a cool white preferentially. The 'grow bulbs' are not necessary and usually more expensive. They are designed to put out more blue light but the slight advantage is minor if the price is much higher.
You could also use the daylight type bulbs Pyro mentions.. they come in various brands.. ultralume, chroma 50 etc. They are usually a little more expensive than the standard cool/warm white but not always easy to find the size that you need. If you can find them and they are not too expensive these types of bulbs are noticably better than the cool/warm white combo.