Anytime you go larger for your frame you are going to look fake. Now I dont know how tall you are and how much you weigh, but given your bra size 34A I would say you are on the narrow side.
550 cc is a big implant and it really depends on how much room you body has and how wide your breast are on your chest. So without an exam and measurements it is a shot in the dark to tell you how you would look.
You really need to meet with a board certified plastic surgeon to go over things in detail.
Good luck.





