The only problem with a new dog in your home would be the neutering! Dogs adapt to each other after an initial period of "getting to know each other." You will have to make sure your current dog gets even more attention than he's used to once the new one is in town. I do forsee more problems due to the fact your dog is not neutered. There may be more aggression if you introduce another male, and puppies if you introduce an un fixed female (du, I know).
We introduced a puppy with an 8 yr old neutered male a few months ago and they now absolutely adore each other. I make sure Rascal (older dog) gets his "alone" time in the yard without Trixie loving him to death. When they are together, they play alot and Rascal ends up getting more excercise than he used to. It's really brought more "life" to the ol man!
