If your only going to be using CFLs you'll want at least 6-8 (more is you can) 40 watters. Those put out about 2600-2800 lumens.

You'll use the "cool" to veg and then have to switch the bulbs to a "warm" to flower.

So you're looking at 6-8 of the cool and 6-8 of the warm.

And I wouldn't let them grow straight up, the CFL's won't penetrate the foliage down low and your yield will suffer. Read about LST-ing to keep the plants lower and increase your buddage.