My Grey, Ruby, is the quietest of our 3 birdies. She never screams and makes wonderful sweet noises. She's started mimicing the birds outside like mockingbirds, sparrows, doves and cardinals.
If we're plugging our favs, I also have to suggest a red-front macaw. Our Jade is so cuddly but she's also very playful....very playful. RFMs (my husband says that means Really Fabulous Macaw) are smaller macaws so you won't have a giant flying about your house. She's also pretty quiet, although louder than Ruby. She only screeches when she's trying to get a game started.
Good luck.