I found my 2 GCCs would line up the other birds and try and take them out. Dharma is quite placcid and either keeps to herself or interacts with Olly. The lorikeets can still outscream her. I haven't had much to do with Nandays.
The thing is that you're getting a young bird so it will be on the bottom of the heap with your flock initially, so a GCC might be kept in line by Chaska and co. I am a little biased but I really do like the suns. Dharma will stick up for herself, but doesn't go looking for trouble.

My young suns can be in harmony with the budgies except they eat budgie nest boxes. I put the suns most days in the outside aviary with the budgies. The older breeding suns are very territorial and will attack anything that lands on the aviary but I think this is simply a breeding thing as even the older ones are not aggressive outside breeding season.