Is it possible to actually make a whole grow with CFLs?

[psteve]

but at some point it is more efficiant to upgrade to HID.

IMO, that point is 225 Watts.
If you are using more than 225 watts of CFL, you might as well be using a 250 Watt HPS. Your plants will be happier, it will generate more light, about the same heat, and use about the same electricity.