Gas is the better option as it dissipates less than a 24 hour period. Safe for your cats as it leaves no residue, though, it is an expensive route. While I don't have the name of it there is an effective solution in which you place one drop of a special concentrated liquid in the ant route and in soon time the ants drop off.
PT is right gas works real good on ants, I've never used it inside though...
I'd send the cats away for a few days until you can take care of the problem. Have someone come in an nuke 'em for you, it'll cost you but it's better than fighting them with over the counter stuff. You have to find the source if you want them gone for good.
i woke up one morning to my cat tossing a mouse at my head...lol. cats will get anything that moves....but, ants are to much. i agree with the bombing of the house or raid.
I'll grab some artificial sweetener when I go shopping tomorrow and give that a whirl, and ring the exterminator on Tuesday and see if they can come out and at the very least find where they are coming from.