If you have the money i would definitely go for a T5 florescent light. Such as these depending on how much room you have in your grow space.
http://htgsupply.com/Product-HTG-Supply-2-Foot-2-Lamp-PL-55-Tek-Lamp.asp 70$
http://htgsupply.com/Product-HTG-Supply-2-Foot-4-Lamp-PL-55-Tek-Lamp.asp 135$
T5 high output florescent lights put off something like 93 lumens per watt, while CFL's put off something like 65. So basically you are getting 1/3 more light which = better results.
It is in my opinion a much better investment than buying CFLs because if you want to get a good yield you need good power. You will want to get at least 100-200 watts for 2 plants and the money is going to add up once you pay for all the equipment. If you purchased the 4 bulb T5 (if you have space for it) you can get very good results. If you decide to go with CFLs you can pick them up locally either 27, 42 watts, or you could purchase 1 or 2 of the big bulbs depending on what your store carries maybe 150watt. During VEG i would stay with the 6500k spectrum but during flower i would add in some 2700k spectrum so the plants get both. This is also a good site for small bulbs.
http://www.1000bulbs.com/