Nobody doubts you love both birds, and that your heart isn't in the right place, however...
You and I both came to these forums for a reason. We're new to owning birds and these people have a wealth of knowledge and experience. We want what's best for our birds, so we sought out the experts (as close to experts as birds can have, since they've not been around much as pets for very long). If we really want what's best for the birds, it's wisest to listen to the people who know more than we do.
I'll tell you a story. Up until recently, I had no intention of getting a bird of my own. Goofy was about as much bird as I could handle. He's MrC's bird and lets me know it in uncertain terms. Honestly, I was afraid of birds, even though I tried really hard to work with him. One day we were at the bird store where MrC gets all his bird supplies. I went into the bird room and there was this gorgeous blue and gold macaw that kept reaching over, wanting attention. This bird was HUGE and based on my experience with Goofy, I was rather terrified of him. On the perch next to the macaw was this lovely little African Grey. I was just standing there talking to the little CAG when the macaw quite literally climbed up onto my arm without an invitation. I was nearly paralyzed with fear, but the shop employee just chuckled and said "Just talk to her, she's a sweetheart." He was right, she was a sweetheart.
I went back to that bird store almost every day for the next two weeks. I was, and still am, completely in love with that bird. I wanted her so bad I could taste it. I even quit smoking so I would have extra money for her toys (and I'm still tobacco free...8 weeks and counting). But I also did a lot of research. The more research I did the more I realized how ill-equipped I was to handle such a bird. She needed somebody who knew more than I did, who has more experience. It wouldn't be fair to her, or me, or even Goofy and Cookie to bring in a bird that I was ill-suited to care for.
So I did more research. I kept looking around for available birds. I found this little Senegal who needed a home. By this point, I was doing research on just birds in general, and felt confident that I could take care of Leopold. I still have a lot to learn, not just about caring for Leopold, but also in helping to care for Goofy (Cookie is easy...such a laid back, chill bird in his twilight years).
As much as I wanted that Blue and Gold, and as much as I would have loved her, it wouldn't have been fair to any of us for me to take her.
These people on this forum, they see these things all the time. They see people with good intentions get over their heads. They love birds and they don't want to see anything bad happen to any bird, even the ones they just hear about on the internet. But they see it all. They see the people who are so happy and excited when they get their first bird turn into miserable wrecks because the bird became a hormonal jerk at mating season. They see people enjoy the honeymoon period so much that they take in more and more birds, until the flock becomes unmanageable and the birds suffer. The see bird after bird after bird get rehomed at best or mistreated (intentionally or not) at worst. They will do anything they can to help prevent it happening to another bird.
They did not advise you to hold off on getting Jazzy because they're mean. They said that because they have experience you and I don't and know what's going to happen as soon as the days start getting longer. They want Carlos to have the best life possible with you, but they know that adjusting to two hormonal birds before you have a solid bond with one of them is a recipe for disaster. They care about your birds and they care about you. That's why they're upset. They don't have to care. They could just toddle off into the sunset saying "good luck with that", but they're not. They're telling you as gently as they possibly can that you haven't made a good choice. You have a grace period in which you can change your mind about Jazzy.
As a non-expert, my advise would be to listen to those people here who know far more than we do and take advantage of that. Yes it will be sad for you, but remember that you're not doing it for you. You're doing it for Jazzy and Carlos.
Even if his love becomes conditional mine will never be. 
