You're fine with CFL's. You can probably get away with about 10-15 100W-150W equivalents for 4-6 plants. What kind of system are you using? Is it soil or hydroponics? So, here's what you do: during the vegetative state, use blue spectrum CFL's, those would be the "daylight" CFL's. During the flowering state, use the red spectrum CFL's, those would be the "soft white" CFL's, but throw in 1 blue spectrum CFL with all your red spectrum bulbs during flowering. If you don't know which is which, you can tell just by buying one of each kind, plugging them both in at the same time and comparing their color. The red spectrum CFL's are going to look kind of an orange yellow, and the blue spectrum bulb will look kind of blue or really bright white. I know last year you could get both kinds of bulbs at Wal-Mart, sold individually as 100W equivalents, for about $1.00 each. Haven't bought any since. The red spectrum had red on the box, the blue spectrum ones had blue on the box. Gee, seemed kind of like they were advocating it.
Oh, one more thing. . . Make sure you use some sort of permanent marker to date your bulbs. It doesn't seem like it would happen, but they do grow dimmer over time. If you're planning on using them for more than one grow, you'll want to make sure you have a mix of old and new bulbs. Also, pick up a cheap pack of the 60 or 75 W equivalent bulbs for back-up. You never know when you might need 'em. Sucks to be without 'em when you don't have one. And get some of those individual sockets that you can plug in directly into an electrical strip, they're about $2.00 a piece. You can usually put about 3 of those into one electrical strip. See, now using that method, you've got a 300W-450W equivalent lighting fixture for around $15 bucks. I did my whole Bubbleponics DWC knock off system, including lighting for about $150.00 total. That was buying everything from Wal-Mart, Home Depot, Lowes, 1000bulbs.com.
The only thing it doesn't include is the nutrients.