Wanting to know people's thoughts. We already have a Border Collie (18 mths) and a Golden Retriever (10 mths) and we're thinking of getting another dog. The next dog we want is a Bernese Mountain Dog, and I'm not sure with the size of it if it would be such a good idea? Also I'd want to get a girl, but our other 2 dogs are girls and don't know if this would also cause a problem?