I don't really know a lot of friends with dogs. The ones I do know have two huge golden retrievers which would terrify my cats (lol), the other has an extremely skittish little dog, and my parents have a very old cocker spaniel that wouldn't do well on a two hour trip to where I live... poor thing is completely blind.
It is a good suggestion though, so thank you for it.
I'm really not worried though. I plan on bringing a puppy in, so the cats should do well around something smaller than they are. They'll just do the usual hissy run away jealous kitty thing, and get over it in a week or so. I don't think it would be that bad of a situation.
I guess my main concern is a yorkie being happy around cats in general, but from what I've read, the pup should be fine.