What's a good cat flea preventative besides the Seresto collar?  

We had a flea infestation last fall because we never had the cats treated and somehow the bastards got into the house.  Daily cleaning and vacumning commenced and we finally beat them.  After that we put both dogs and both cats and the collar and haven't seen one until about 2 weeks after I had to take the collar off one of the cats because she was scratching herself really bad, to the point she was getting scabs around her neck. 

Advantage II gave my cat seizures.

We use Frontline. Even with two dogs bringing who knows what in the house (indoor cat), it works great. Dogs are on K9 Advantix II.