People are not coming to conclusions about you, just answering the question you asked... you asked if you would need to sell one bird to keep another... bad question to ask a bunch of bird lovers who live their lives and organize their home to keep different species safe.
And before I get into the rest of the response... no, don't buy a macaw, go to a shelter / rescue and let an adult macaw PICK YOU... no more rewarding relationship then an adult macaw deciding you are their person. When the bird picks, its never a bad match
Emotional response aside and pretending you did not actually ask about one bird going to keep another... facts and reality about having different species...
Many many homes have different species. In my home we have budgies, cockatiels, green cheek conures, sun conure, bare eye cockatoos, Senegal, amazon, blue and gold macaw and a Grey foster. Much like having more then one kid, you need to have the time, love, patience and space to keep each of their children happy. My macaw is very bonded to me, he is literally a momma's boy. But, he is so well loved and spoiled, he does not feel threatened by another bird. I don't put him away because the bare eye cockatoo Ivory is out. They are both out and socializing at the same time, but never with each other and we have the space and areas to allow each to have their own space. Opposite of the 'norm', my cockatoo prefers to be up high and is on playstands most of the time; while my macaw thinks he is a blue and gold puppy, he spends almost all his time playing on the floor.
One thing to consider is having a dusty bird in a home with a macaw. I'm not an extremeist to say no, never. Just be aware and safe. Ivory has an Austin Healthmate air filter literally sitting right next to her cage and her cage is on the far wall in the large country / eat in type of kitchen opposite what would be a breakfast nook (instead of normal furniture in the beautiful bow window area, I have a very large java stand). And Max the blue and gold has his own bedroom one floor up. So at night, Max is not breathing air that may be dusty from Ivory.
But just like anything in life, what you put into relationships is what you get out of it. If you are bonded to your galah, I would hope your instinct and feeling is that you need to find a way to keep your first baby with you, but have room in your home and heart to welcome another feathered family member. I've had moments of doubting whether having a bare eye too is the right choice for my home, but its nothing to do with the other birds, its dealing with her behaviors and the limits I have to deal with sometimes because of my health. But, tho the easy path would be to 'rehome' her, I know I would regret that decision and miss her like losing a child. So, much like having a kid you don't quite understand, you support that child and find a way to keep the family happy!!
Hope this helps some.... but please, without being mean or jumping to conclusions. If you truly do feel that selling one bird to get another is the right thing for you, please think about how intelligent and emotional parrots are... I can personally share with you so many heart breaking stories of how birds are when they come into the shelter and how they literally can mourn the loss of their family.
Best of luck with your decision!
