I don't like to just flat out contradict people but I must disagree with Valydius on one point - a high CRI is not appropriate for plants. At least, "the highest possible CRI" is an inappropriate criteria. CRI and color temperature are factors having to do with the average color the light puts out. Plants can use light coming from several ranges, so there isn't a single color that you're looking for. (Besides which, "the highest possible" is stuff like UV radiation, X-rays, microwaves...) A lot of growers here report good success with a 50/50 mix of cool and warm white fluorescent bulbs, which are typically rated 6500K and 5000K, respectively. A higher color temperature won't necessarily be better for your plants. (It's also worth noting that, going by reports here and on other growing forums, fluorescent lights sold specifically as "grow bulbs" are no better and often worse than ordinary warm/cool white bulbs.)
If you really want to find the best light out there, the number you need to optimize on is the photosynthetically active radiation (PAR.) PAR is a measure of the energy in light weighted by its usefulness to plants (so energy in the form of green light, for example, is not included in this measure because plants can't use it for photosynthesis.) Unfortunately, very few bulbs are rated in terms of PAR; the best you'll probably be able to do is to look for independent lab tests and use them as a buying guide. Or, if you know the physics staff at your local university, you may be able to obtain a photospectrometer to do your own research. In any case, the next best thing to look at is lumens, which is a measure similar to PAR but biased towards light visible to humans (note that humans see very different light than plants.) By comparing lumens with respect to electrical consumption (watts) you can get an idea of how much energy the bulb actually sends out as light. Search the forum here for terms like shop lights or PAR and you can find a lot of discussion on the topic. In my experience, four or eight foot shoplights with 40 watt T12-size bulbs are cheapest and most efficient because they're the standard for industrial applications. The rest is a matter of finding good prices and quality bulbs. Remember that fluorescent bulbs lose a lot of power after the first six months of operation, so a cheaper bulb might be worth it the price means you can replace them regularly.
~Joe
PS - Also, when it comes to the CP FAQ, keep in mind that Barry is sometimes kind of a worst-case-scenario type of guy. Modifying your lights is probably not necessary... I don't know a lot of people here that do. I consider my shoplights to be free space heaters, as Washington is a little on the cool side.