With more than adequate filtration and plenty of hiding spots, I have had great success with keeping other fish with the JD. There again, my JD has always been with other fish and I think that makes a difference. Imagine yourself always living alone, and suddenly, you have 5 people move in with you!
Really, it depends on the temperament of your JD. From what I have seen they have different personalities. Where mine isn't aggressive at all, yours very well may be. It's all trial and error. Most large cichlid keepers have what they call dithers in their tanks. Hatchets are commonly used and other fast moving tropicals. Bear in mind these fish may get eaten or beat up, depending on your JD.