I have heard good things about Colby dogs. Have not had the pleasure of seeing one working in any capacity in person though.I admit I know little about APBT's, but definitely learning more. I think the only well known line I can name off the top of my head are Colby pits, which were even used in some OEB breedings. A friend of mine has an OEB with Colby blood, insane drive on that dog. It's the oldest and best dog he owns.