It's always a crap shoot introducing new birds to the household. Quakers are known to be cage protective, so you can probably know that a new bird that ventures near his cage will be dealt with in a rather harsh matter.
My littles share our front room, with their cages sitting right next to each other. The budgies control their cage and the area on top of it. No other bird is permitted in their "space". Violation of the space results in bites from the budgies.
The tiels share two cages,and it is a true sharing thing. They will sleep together...or sometimes one wants space and sleeps alone. All food in the cages are shared, which presents a problem for Buddy, our Nanday. He is very food protective, and will drive off any tiel that dares try to steal food from his cage.
With all these rules, will still have relative peaceful co-existence with the littles...they know the rules, so they follow them...