best guard/defence dog

[dec11]

im moving out of the city to the countryside within the next 3mths and as i work nights and sometimes go and visit family who live 200 miles away i need to get a good guard dog as the missus is quite afraid on her own at night.
now i know most would say rotty, german sheperd, pitbull etc but i dont particularly like those breeds.
im down to the following

1. rhodesian ridgeback
2. boerboel
3. cane corso
4. poss other type mastiff


it must be able to get on with my 2 dalmatian bitches, i will be getting it from pup so im hoping that wont be a problem.
i want the dog to be able to go at an intruder rather than just stand and bark.

anyone have experience of any of these 4? cheers