Yep, my female nic was a b&*ch, killed her sibling and went on to terrorise everything else in the tank, including severums, aureus, geophagus and this was in a 125g tank, however, they arent all like that, so its like any other cichlid, some are peaceful and some can be real rogues.
I guess I really just have to be more flexible and see the nature of the fish when they're settled into the tank and go from there. If it comes to it and things aren't working I can pass fish on to other people on here or LFS and then consider a different option within the constraints of the other fish that will be in the tank at that point.