Your opinions on good dog breeds please
My breed of choice is a Rhodesian Ridgeback. I've had three of them and they're absolutely the best. Short hair so shedding isn't much of a factor. Very rarely bark unless there's something to bark at like an intruder - they're not the nervous type that barks at every little sound. Also extremely loyal. They will usually select a primary member of the family and lay down their life if need be for that person.
Our current Ridgeback is a lean well-muscled 92-pound couch potato most of the time, but he's up and at the door if somebody even approaches it. His deep bark is enough to keep any intruder out. He's really a very friendly gentle dog but is big enough to be intimidating even when just taking him for a walk.
Good luck in finding one. You might try a local rescue organization like www.ridgebackrescue.org if you're interested in learning more.