Theres really no way to tell at this point it all depends on how big you allow them to grow, how healthy they are, and what strain they are. I would say if you did everything "right" maybe close to a 2/3 Oz each depending on the strain (I've gotten some large yeilds from Purple Kush some strains respond better to CFL than others). Also you want to use the 6500k for vegging only not so much for flowering, when it comes time to flower switch out all the 6500ks for 2700ks. I've done alot of CFL growing its great for stealth but the yeild is not as much as more powerful lights and the buds usually come out really airy (or fluffy) not dense. Also make sure you keep the bulbs between 5-7 inches from the plants to get the maxium benefit.
Good luck dude!
P.S you'll need at least 10-12,000 lumens for that space or about 7 bulbs