doberman and perhaps other breeds? The dog is supposed to be huge and look somewhat like a pitbull. I think the breeds were rottweiler, pit bull, doberman, bull mastiff and perhaps a great dane, but I am not sure.

You are exactly the person who would NOT get a dog from a reputable breeder.Is that all you care about? Size?

Anyone who mix breeds dogs on purpose, Is a complete moron!!

Yes, it's called a big MUTT!