I don't know much about breeders but, i have heard terrible things about Sanders in many places including this fórum i think, i have heard many good things about Bravo but they work acording to FCI standard wich have little to do with working lines, you can tell just by looking at their dogs, Presa Mania i know nothing about. If you are looking for working lines you should try to find a breeder who work according to a more tradicional standard(there are many of them) in the US, if you are there, it will be UKC breeders, theirs it's the more "tradicional" one. Good luck.