MAKE NO MISTAKE ABOUT IT, THIS IS BY FAR THE WORST ADVISE EVER GIVEN ABOUT DOG TRAINING. YOU SHOULD NOT BE ALLOWED TO OWN ONE.
Get a sprotdog 1800 electric shock collar, charge up the battery set it to the highest level place collar on dogs neck, wait for dog to go for cats hit the juice button hard let it burn in. After a few of these that dog will leave the cats alone. In a dog fight however it will keep them fighting as the shocked dog thinks the other dog is doing that to him so be carefull.
I train dogs on a daily basis for both my self and clients. I use E-collars every time my dogs come out of the kennel and most of them can't wait to put it on since they know it means they get to work. An E-Collar is a correction tool not a training tool. The dog has to know why it is getting the burn so he/she can turn it off. A collar should never be used out of frustration or anger. I think every dog owner should get trained how to use a E-Collar and how to use it right. They are great tools when used correctly.
If you look within your community you will find many jobs for your dog to do that require very little training. However, nothing beats hunting with a well trained dog, it is very rewarding. Good luck with your new pet.