Equivalent! I also have 4 100w 6500k for veg. The 100w flower bulbs are 2700k. Both put off 1600lumes as well.
Impossible!! You can't have too much light. You can have lights that get too hot, but not too much light. The more light, they bigger and better they grow. Make sure your CFLs are the correct spectrum for veg/flower...whichever you're in the process of doing. Will warn you that CFL's don't make the fat juicy buds as well as HPS or LEDs. But they will make flowers. Just not as nice as with using the other lights. Your biggest problem is going to be getting the heat out of that big. Anytime you grow in a confined space like that, heat is always the issue....even with CFLs. So get everything setup with fans and ducting so you can pull the heat out of there and not kill your plants. TWW