Thinking of adding a new puppy to our family

I am already a happy owner of a 2 year old male Miniature Schnauzer and I am wanting to add a new edition to our family. I am not sure which would be a better edition a male or a female or if it matters at all. He is a very calm submissive dog I could not have asked for a better dog. He has many female friends that come over and play and they get along great. He has not been exposed to many males but the ones that he has come in contact with have not seemed to care for him. I have heard that a female's personality is much different than a male's and I love the nature of my dog and would like to get a puppy with the same temperament as his.