I grew 12 plants under one 4ft fixture (2bulbs) and in 30 days they were 1ft-1.5ft
I had the lights 1inch from the tops, no fan most of the time, and 24/7 lights.

Wouldn't recommend it but it WORKED.
Ebay has some pretty nice CFs. 125w 8,000+lumens for $70. Kind of expensive but I think i'll go with these instead of a hps setup. hps is too hot, ventilation has to be dealt with and I'm scared i'll get caught in an apartment with a hps setup burning so much electric.