Would you say your poicephalus are the most quiet. Right now I'm looking into brown heads. I finally found one. My house is very tiny at the moment lol.I worked night shift 20 years with 12 tiels, four budgies, two lovebirds, two green cheeks, three Poicephalus, four canaries and one African Grey. Once you get used to the sounds the birds make, you will sleep through just about any sounds they make! In truth, my 12 cats disturbed my sleep much more often than the birds.
I love the Poicephalus species which include the Senegal and Myers, and Cockatiels. My favorites.