I have 320cc moderate profile implants. What cc size can I achieve with high profile or moderate profile plus?

Just changing the profile does not increase the volume. However, it does increase the forward projection of your breast and decreases some width. You may find changing the profile to a higher profile give a better look and may fit bras better as well. Choosing implants that are too large and heavy for your frame leads to future problems of bottoming out, thinning, and sagging. Your surgeon who has examined you was trying to give you the best long term look for your tissue and frame. Not all women can or should be C+, ++, +++ sizes.

Dear Doramom1,
implant profile is a very important consideration. Many patients wrongly assume that the higher the profile the better. The truth is, the more profile (or projection/height) and implant has, the narrower its base has to become. This has several problematic consequences. The first is that the patient loses width and therefor cleavage of the breast. The second is the breast becomes more narrow and pendulous, often falling lateral and onto the side of the chest, and third, high profile implants have a higher risk of bottoming out because they exert more pressure on the inframammary fold than moderate profile implants. High profile implants do have a role in symmastia repair (when I need to narrow the basewidth) but otherwise I try to avoid them.
Daniel Barrett, MDCertified, American Board of Plastic SurgeryMember, American Society of Plastic SurgeryMember, American Society of Aesthetic Plastic Surgery

Unfortunately, you have not provided photographs or told us your bra size. However, if the implants are placed retro-pectoral then the profile does not matter that much because implants are compressed by the muscle. The change in profile may not give you the desired goal. You may need a lift but I would need photographs to give you an accurate answer.

Best Wishes,

Gary Horndeski, M.D.