Hi Chris,
Better not.
The good thing about the collars is that they work quite reliably and also for to work against flee jumping on the pet in the days afterwards.
The disadvantage of means like sprays and powders that are being applied all over the pelt on the other hand is that you have a much higher incontamination, especially with cats as they do lick / clean their entire body several times a day as you know. ( Another reason for lesser primare efficiency as well.)
Now that the frontline stuff has been applied already I wouldnยดt go for additional collars though, for chances are that it would make too much poison altogether. ( Could result in whatever consequential deseases and pain from allergies, asthma to cancer that might be breaking your heart and wallet in the future.)
If you donยดt experience noticable relief inside the house within say the next 10 days or so then itยดs certainly about dog flee, and you should consult a vermin exterminator. ( And it would probably mean that you had to treat the cats again too. )
I suppose there is no chemically `healthyยด way out of it to treat the house, but Iยดm sure that there occure better and worse ways, so hopefully it shall be a pro who cares for clientsยด health and updates himself regularly on his job. ( I mean none of the olยด fashioned "Naaah, it wonยดt hurt anyone"-types with craters all over their face skin.

)
Ruphus