If you have had complaints about the parrotlets, you will need to be very particular about another bird and noise. I would definitely rule out a sun conure. Sun conures are loud birds. There is no changing that.
I have a linnie. She has a contact call that is piercing, and if she is separated from the other birds, or if she hears a bird on the computer, she will contact call. She talks a lot, and the talking is not too loud. She also makes cute giggling noises. I read on another thread that you have become interested in linnies. If you are seriously considering a linnie, please visit or join the linnie forum before you get one and read as much as you can about linnie noises. They have a poll on there about linnie screaming and much information. My particular linnie does not scream as long as she is housed with another bird, but she screams often if she is not. Not all linnies are like that, and yet it is fairly common. ALMOST ALL linnies contact call when you have multiple birds in the home and you take the other birds to other rooms or when you play sound clips of other birds. You must expect this if you get a linnie. The call is not something I can hear if my linnie is at one end of my house and I am at the other end, but I do believe it is louder than a normal parrotlet sound. My linnie is very obedient and sweet, so please don't take this reply to mean that I am saying linnies are not good birds. I just know that there is a ton of great information about linnies on the linnie forum, and I would want you to be well informed before you made a choice. If you decide you want one, there are also breeders listed on that forum. Also, I do not have a creamino or lutino linnie myself, nor have I ever actually seen or handled one, but I get the impression that particular color mutation may be slightly milder in personality than the other colors. Don't take my assumption to be true. It would just be something you might ask about. It could be totally false.
I also have a green cheek conure. I am prejudiced toward her, so my information on her will be somewhat biased. She is NOT quieter than a parrotlet, and she is about as noisy as most linnies. However, she is still a quiet bird as far as birds go. Her call is slightly lower pitched than the call of a linnie. She happens to scream very little, but green cheeks can scream if they want to. She just doesn't. I would much prefer my green cheek to scream full volume right into my ear than my linnie.
Both have. Both experiences are unpleasant. The linnie scream is simply higher, and, therefore, to my ears, more annoying. If you do go onto the linnie forum, read threads on there by Crystal about her noise issues with her apartment neighbors. She has had complaints from neighbors about her birds' noises. Her conures happen to be louder than her parrotlets and her linnie. I can't recommend green cheek conures enough when it comes to fun. My Shira is very entertaining. She loves to be with me, but she has a great time with herself and her toys when she cannot be with me. When she is with me, she plays hard and fast for a time, and then she crawls up into my collar and snuggles against my neck and hair for a cuddle or she crawls into my hands for a scritching session. Shira is a pineapple green cheek, so her colors are not quite as vibrant as the colors of a sun conure, yet she is still quite visually exciting. All of the pyrrhura conures would have very similar personalities and noises, so you would not be limited to green cheeks if you wanted to go with a small conure. (By the way, Crystal posts sometimes to this forum. If you look through Talk Parrots you can find her user CP and perhaps contact her right in here. She has two parrotlets, a linnie, and two green cheeks. She has had other linnies in the past.)
If noise is a serious consideration for you in your apartment, and I think it might be because you've already had complaints about the parrotlets, I also have to recommend Australian grass parakeets. They are not silent, but they are quieter than either linnies or pyrrhura conures. They can be very interactive. Many are not because people have considered them aviary birds, but hand-fed birds that are interacted with often can be very tame, and they can crave human interaction. My daughter's bourkes is one of those who does. They can also be quite beautiful in appearance. They are not cuddly the way conures are cuddly, but they have their own charm. My daughter's bourkes enjoys petting more than my son's linnie. They are more similar in actions and personalities to budgies than parrotlets are. Many people on this forum have grass parakeets, and there are threads about them on here. The most easily found grass parakeets are usually bourkes and splendids, also known as scarlet chesteds, and you will sometimes also find turquoisines.
My daughter also has a maximillian pionus. They are sweet, but I absolutely cannot recommend a pionus as an apartment bird in your particular situation. They have a call they make to great the dawn and also whenever they feel abandoned, and it is quite loud. A pionus is basically just an overgrown linnie, anyway, so if the tractable, fairly sedate personality attracts you, as long as you live in an apartment, a linnie is a better choice, although, as I have warned, I think linnies can be louder and more piercing than parrotlets.
Jenny, a moderator on Talk Parrots and the Linnie Forum, has a great deal of experience with all of these birds, too. Perhaps she can chime in, although I believe she is perhaps swamped with life responsibilities for the time being. She has posted much great information on both this forum and the Linnie Forum about all of these birds and their noise levels. It would be great if you could look up some of those posts.
Aside from the noise issue, which is paramount, do you have a preference for a certain type of personality or special interactions you would like to have with your new bird?