And by the way, I'm also completely serious about the dogs. We have Australian Shepherds as my wife competes with them in obedience and herding competitions. That said, the dogs also have passed protection tests with flying colors, actually embarrassing a number of German Shepherd owners in the process. They are "reserved" with strangers but happy as hell with friends. As long as we're not showing any nervousness they're friendly. But the moment they sense any discomfort or nervousness in us, they change modes quite quickly. I was annoyed as hell one day as a guy came up to my house when I was in the middle of something else and in a foul mood. The guy wanted to sell me something and was rather insistent. But when he noticed both dogs go from quietly watching and wiggling to rather obvious deep growling, he decided to pass on trying to convince me any further...
Oh, and make sure your "grounds" around you house are well lit and if possible easily visible from the street. Anything to make it less welcoming to bad guys...
Dogs always notice the mood of their owner. If you are nervous, your dog will recognize that and react as expected. A dog is always a good thing if it comes to protect your home. But not everybody has got the time and the affection to care for a dog.
Especially Australian Shepherds need a lot of training and engagement or they will become a huge problem for their owner.