I currently have 10 tiger/ruby barbs in my 75 gallon with an angelfish and 2 gouramis and they are doing fine. The angelfish and gourami are on the large side however. There are other smaller fish in the tank as well and the barbs leave them alone. I've seen one or two pick at the other species occassionally, but it's the normal kind of stuff you see all fish do in a community tank.
The key, in my experience, is to put them in a big enough tank and a large enough group so they can't focus on one fish and pester it to death. I think 8 would be fine as long as there is enough room for them to chase each other and not collide with too many tank mates.
Edit: I also want to mention my tank is fairly sparsely planted at the moment, with some fake plants and one real one, but they still don't bother each other. I did notice in my 10 gallon though, the plants helped to allow one to go hide if he needed to.