Our outside/feral cats and kittens can go in the heated garage thru a dog pet door. The door got a lot of abuse when we had a dog. We no longer have one. There isn't much of the flap left. Magnet is totally gone. I need to replace either the flap or the entire door soon as winter is on our door step. Would a new dog door be too difficult for the cats to get open? Or should I go with a "cat door"? Prices are about the same.