I wouldnt replace anything at all. I would definitely invest in an hps for flowering. CFL's aren't as high intensity as HPS so it doesnt penetrate the buds as well An HPS will give you nice dense nugs where as a cfl will give you more fluffy loose buds. Not sure if this means that the dense buds will be smaller and the loose ones bigger or what, but i know for sure that if you have to buds side by side the more dense one is going to be heavier. Its common sense. So weather or not they give the same weight with the same wattage? i doubt it. I would be willing to bet hps would get you much heavier yield but of course you will have heat to deal with and such.
I have 4 plants under 276 watts of cfl's and a 54 watt t5 giving me somewhere in the range of 330 watts. I think a 250 hps would be perfect for flowering this amount and maybe not get to hot as well? not sure tho, im not an experienced hps user. Heres my link to my journal:
https://www.rollitup.org/grow-journals/479255-dopeys-cfl-closet-grow-fall.html if you wanna see what i got for a cfl setup in my closet. i could flower with it but i would need to buy 2700k and by then i could afford to put together my own ballast and 250 setup i think then i would have the shit i need for my perpetual.