I wouldn't say they're headquartering in Congo. I wouldn't really say they're headquartering anywhere, but if they are, the most likely place is probably Rwanda. The opposition, I'm talking about armed opposition now, is fragmented, quite divided internally, and apparently disorganized as evidenced by the failed coup attempt last May.
Since then, a couple of new armed opposition groups have emerged, including one called FOREBU, which is led by the military officers who participated in the coup attempt. There are others and it's not clear to what extent these groups work together, or are in some kind of rivalry with each other. Many of their leaders and members are believed to be in Rwanda, but not all of them. Some of them float around between different countries. It's quite amorphous and quite diffuse. It's difficult to be more precise about it because even the structures and their location are not that clear.