You have my sympathy - I'm going through this nightmare at the moment too.
I was advised on another thread that it's better to treat the cats with the spot on called Advocate rather than Frontline. The fleas seem immune to the latter. The first night of putting Advocate on them I found dead and dying fleas where they'd been lying.
I also flea bombed the house with foggers - don't bother with Johnsons! I used that and then returned to the room where they seem to be and they were still hopping about like normal. The very next day I bombed the house again (I know you're not meant to but I want them gone!) and this time sprayed round the carpets and nooks with an aerosol spray.
*touch wood* it seems to have got most of them but I'm still finding fleas on the cats when I comb them too and today I found one in one of the traps I've set (if you lay a while shallow dish with washing up liquid water in it the fleas will be attracted to the white and drown in the water) I know what you mean when you say you want to retreat the cats now. I only did mine on Monday but since it was so effective in that first night I want to get rid of the remainder by doing them again!
It's got to the point where I'm scared to have people round in case fleas jump on them! The worst thing is they only started being in the house and jumping on me AFTER I'd applied the frontline!!
In closing, does anyone know if the Advocate makes the fleas sterile or can they still lay eggs after the cat is treated?
Also hoovering before treating the cats can make the problem seem worse because the vibrations of the hoover can make the eggs hatch.
Good luck with your situation anyway. I really do feel your pain!!