We have both Aussies and Shelties in our family. Aussies are wonderful dogs, but they do best with more people attention and they need more exercise than a small dog is going to need. If you can find the right lines they would do okay as apartment dogs (my Dad has a female that has always been extremely mellow).
If you like Aussies, a Sheltie would be an option. With a Sheltie you have to watch who you get them from. You want a breeder who is aware of what correct temperament should be for the breed. They need to be well socialized and you need to take time for training. Most herding breeds do bark more than some other breeds (not all). I raise Shelties (the Aussies are my Dad's) and mine are not crazy insane barkers. I've placed quite a few pups in apartment homes and they do very well as long as their families take the time to train them as puppies. Shelties also don't need as much excercise as an Aussie. They are usually pretty content with a 30-60 minute walk each day or some fetch time at the dog park several times a week.
Aussies and Shelties have some definite differences in their temperaments, but I think an Aussie is like having 2-3 Shelties all rolled into one dog. :)
Female Aussies can be smaller. You can also look at getting a smaller female from the litter. Some breeders also raise "Mini Aussies". If you can find one that is not compromising the structure of the dog, you can find reputable breeders who raise them. Mini Aussies tend to be more in the 30 lb weight range.
I know you might laugh at me but teacup my chi is the best guard dog to have . he barks only when some one is at the door he alarms me if someone is at the front or back of my house. he cries for everything else toys,food, or to go out side etc.. hes a strange little dog but we love him to death. get a chi...