cfl and lumens help needed

I have been doing some research on this website about the proper lighting and I have a few questions.
First, I read that 7,000lumens of light is required per square foot. If my growbox is 2' (l) x 2' (w) then the square footage of my growbox is 4 square feet. 7,000 lumens x 4 square feet = 28,000 lumens. This means that my growbox requires 28,000 lumens of light to properly grow my plants.
Second, I read that cfl bulbs range from 50-70 lumens per watt. For this calculation I will be generous and use 70 lumens per watt. A 100 watt equivalent cfl bulb that is 23 watts provides 1600 lumens of light.
So, if my grow box requires 28,000 lumens of light and the 23 watt cfl bulbs provide 1,600 lumens of light, this means that my grow box will require 18 cfl bulbs? (28,000/1600 = 17.5)
Is this overkill for 1 plant that I intend to grow in a single bucket dwc setup with the scrog method?
If so, how many cfl's should I use? HID lights are not an option.

The general rule of thumb cfl I was told while I used them was 100 watts for the first plant and 50 watts per plant after that. So if you got three plants and your using the 100w rated bulbs which are really 23w you would need five bulbs and then two to three bulbs after that so you'd be looking at 10-11 bulbs for a really good grow with cfl and it really helps to move the light all around the plant as the cfl light doesn't penetrate the canopy well and the number of bulbs it doesn't change from veg to flower with the 5000k to 2700k but the more the merrier lol

Here is some info on scrog I've used

http://www.treatingyourself.com/vbulletin/archive/index.php?t-12326.html