@Dropbear 

You are almost there. Go to devices, select the existing router, go to config and choose forget.

Go to admin wired network and changed the router type.

You can then adopt the new router and it will load the existing config saved on the OC200/OC300 and provision/configure your new router. You may have to choose some options when adopting as it transfer over the config as the model has changed. 

That's the process I used to upgrade from ER605 v1 to ER605 v2 so it should be the same. 

  @KimcheeGUN and @Lurk - just want to see if I am following correctly.

1. Update the IP settings on the new router to the same as the old router, via the web management tools (192.168.0.1 by default)
2. In the controller, go to the current router | Manage Device | Forget
3. Plug in the new router and adopt

That's it? The controller will know to load the last router settings to the new router?

Much thanks in advance.