CO2 doesn't need extra light, a low light tank can greatly benefit from the addition of CO2 without having to increase lighting. It the type of plants you wish to grow and the amount of work you are willing to put into it that should be dictating the amount of light to buy. If you stay in the 2WPG range you can grow just about anything with CO2 yet still keep things relatively simple. CFs are brighter than normal fluorescents of the same wattage, however the WPG rule has many other inconsistencies that you can still use this rule safely with any fluorescent light. In any case, it's just an indication, not a preceise measurement.
As long as you use full spectrum bulbs, the color temperature matters little other than personal taste. Most use bulbs in the 5500K - 8000K range if used alone. Mixing different bubls will provide a better spectrum and you can personalize the overall color of the tank. 6700K are popular, they bring out the greens very much but tend to wash out reds. The GE AquaRays really bring out the reds but give a little yellow tint to greens. I use a mixture of both.
Hope that helps