After really researching them a lot and not finding tons of consumer input, I went with the one that seems to be best for the multi-animal population. I am still very concerned about my cats getting out. I will maybe see what goes on, and then, put collars on the cats that I am concerned about and add a little electrical current thingy near the door temporarily to train them to stay away.

Here is what I purchased:

http://www.k9electronics.com/product...gePetDoor.aspx

This seems like an install job for a 'professional'. I will call the contractor I use for home stuff.