The reason you get so many different stories is because different people have different results. Sometimes people have problems integrating new BO's into a flock of BO's. Some people mix about anything with no problems whatsoever. I don't know which one you are. There are so many different variables, some you can control and some you cannot.
If you want them that badly, get them. Then deal with whatever happens. It may work out great, with your set-up it sounds likely. You may need to get rid of them (or your others), you may bury them, or you may need to keep them separated forever. Life does not come with guarantees, it comes with opportunities. Sometimes those opportunities have issues. That's just the way life works. How badly do you really want them?