I have been following the boxer discussion with interest. I have two Belgian Malinois myself, and adore this breed.
If you are going to be a 2 dog family, it is wise to have opposite sexes. The female will run the roost eventually, at least as far as food and the house is concerned, but will happily play back-up when it comes to challenging intruders or "furrin" beasts.
There is nothing worse than two bitches who fight all the time. Some have been known to fight to the death, while males will stop when it is clear that one is dominant.
So you think it'd be safe to get a girl for our dominant male? Salty has a Napoleon complex, and likes to bully smaller dogs, but he respects big dogs.