well i have basicly the same set up as you i am using 6 cfl's that are all 150 watt replacements witch make them 42 watt lights basicly sence there soo low on amps all you have to do is add all the lights to gether and see how many amps your braker is most likely a 15 amp add all the amps together and three you go

personaly i think you could put atleast 20 lights on one circuit

wire size i would go with size 10/2 its thicker than 12 or even 14 your probley using 12 awg wire drop it down a size so your wire dosent over heat witch also i dont think but safe then sorry!!

i also use cfl's for flowering it works fine

goto home depot and they got the big cfl's 2600 lumens each thats really good light i tell you this everyday my plants grow atleast a half inch!!!

low on heat and low on power and very bright i have six and when i look in my grow box and then walk around the house im freakin blind for 5 min after walking outa there

how many lights do you wanna hook up how many plants are you growing?