I've owned poms, poodles, yorkies, and maltese and they aren't really calm dogs. You have to take into account what the dog was bred for. A Yorkshire terrier was bred to kill rodents. Maltese were bred for companions. I can't remember what the pom was bred for but you need to consider that a pom has a double coat and it sheds alot! (Even with brushing.) A yorkie and maltese don't shed like other dogs they shed more like humans. Poodles in my expereince are hyper dogs also. I don't know about Chihuahuas since I've never owned or know anyone who has owned a chi. It sounds like you've narrowed down your choices. Good luck picking a dog, it is a hard decision. You've picked some great breeds.
