So, having lived with 3 amazons & 1 'Too, I am obviously biased. I love 'Toos, too. When they flip up their crests and bounce, it always makes me smile.
However, I will probably never live with one again. If you have your heart set on a 'Too, here are things to consider:
1. Are you in an apartment or a house and do you live alone [and if so, do you expect to EVER live with someone else]? All 'Toos can be very loud. Some have a pitch to their voices that almost make your ears bleed. And I'm referring to several of the sulphur crested variety. So if you are considering a 'Too, make sure you hear it scream & know in your heart that you can live with that scream [even if it goes on for a half hour or longer]. And if you live with anyone or might some day, they need to go along and agree they can stand the noise. And if you are in an apartment, your neighbors need to be willing to listen to the same thing. Otherwise, you will most likely be just taking a cockatoo temporarily & putting it into a rescue because you or someone else cannot live with the noise.
2. Have you - or anyone living with you - any breathing issues, like allergies, asthma, or the like? 'Toos put off massive amounts of powder. Some other parrot species are also sensitive to the 'Too's powder, as well as other house pets. I have an Austin Allergy Machine for an air filter. It cost more than $500, but was an excellent investment. If you have any powder birds like 'Toos or Greys, a good air purifier is a must.
I sometimes see Austin air purifiers of various varieties on craigslist, ranging from $60 to $200. Bear in mind that their filters last +/- 5 years & cost > $100 to replace. But that comes down to about a little over $20/year for clean air, after the initial investment & they last forever. There are cheaper air filters out there, but your health is a place to go for quality over price, when possible.
3. You already have one 'South American bird' in the house. If you look at pictures of 'Toos in the wild, they are always - always - with other 'Toos. If you look at Greys, you will see the same. Old World birds - those from African and Australia & Southeast Asia - flock with their own. I think that is one of the reasons 'Toos sometimes have trouble adjusting to homes where there is quite literally no one else who speaks their language. The South American birds, on the other hand, are party animals, and you often see pictures of them in mixed flocks at the clay licks and elsewhere. An amazon and a conure are a more natural pair than a 'Too and a conure.
So my vote [on this amazon forum] is for the amazon

. . . but best of luck, whatever you choose.
[P.S. - if you feel you cannot live without a cockatoo, cockatiels are true mini 'Toos, the right size to live with a conure, quieter than their larger cousins & give off relatively less powder. They don't bounce as much, but their crests are still darned cute!]
