I didn't mean to imply that a small yorkie (or tiny) can't get along well with a bigger cat. I know know that alot of memebers here have big dogs and they get along great with their yorkies. You know your cat best, so if you think it'll get along with a dog then I'm sure it will. I just wanted to point out that yorkies come in many different sizes so you do have options. I also want to get cats in the future.
I hope everything works out well for you.