450 or 500cc? Currently a B?

Examination is critical.  For instance.  If you have widely spaced cleavage with wide insertion of the pectoralis muscles and engage in strenuous use of your pectoralis  muscles, avoid sub-muscular placement.  The medial muscle insertion acts as a wall, and the implants are progressively forced toward the arm pits as size is increased instead of filling cleavage.  You will generally get a better result with silicone on top of the muscle in these cases.

 A common misconception is that the shape of the implant determines the shape of the breast.  In reality, the breast tissue shapes the implant if it is a soft pliable gel.  An implant hard enough to shape a breast is not particularly pleasant to the touch.

There is no such thing as cup size.  If you buy ten bras, you will be a C in one, a D in another, and a B in another.   We like to think of a full "C" small "D" look, as a full but natural proportion to the body shape of the patient.  There is no way to measure it because every patient has unique proportions.  A 500cc implant in a 4 foot patient might be grotesque, yet too small for a broad shouldered athletic 6 foot woman.

Don't get hung up on cc's.  A well trained surgeon will place sizers into the pocket during surgery.  We like to progressively enlarge the breast with sizers. The breast enlarges symmetrically at first.  At a certain point the lower pole cannot stretch any further and the upper pole enlarges disproportionately until it looks unnatural, or the nipples point down.  We then back off one size and this gives us what we call "classy but juicy" in the patient with normal but small breasts to start with.  Drooping nipples, ptosis, tuberous breasts, severe asymmetries, etc., demand more sophisticated analysis and surgical options.  Be sure to consult several surgeons and chose  one that best evaluates your anatomy and offers common sense options.  Best wishes, knowledge is power.  Luis F. Villar MD FACS

   In general, for an average woman 200 cc increases bra size one cup.  So 400 cc would be two cups.  I would recommend trying on sizers in the office to get an idea.  Find a plastic surgeon with ELITE credentials who performs hundreds of breast augmentations each year.  Then look at the plastic surgeon's website before and after photo galleries to get a sense of who can deliver the results.  Kenneth Hughes, MD Los Angeles, CA

Despite your excellent description of body type and goals,  it is not possible to give you specific advice without direct examination or at least viewing pictures.   Ultimately, careful communication of your goals, careful measurements (dimensional planning),  careful selection of appropriate breast implants and skillful execution of the procedure will be important steps in achieving your goals.
 
Generally speaking, the best online advice I can give to ladies who are considering breast augmentation surgery ( regarding breast implant size/profile selection) is:




1. Concentrate on choosing your plastic surgeon carefully.  Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you're looking for. Ask to see lots of examples of his/her work.





2. Have a full discussion and communication regarding your desired goals  with your plastic surgeon. This communication will be critical in determining  breast implant size/type/profile will most likely help achieve your goals. 
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. I have found that the use of words such as “natural”  or “full C, small D cup ”  etc means different things to different people and therefore prove unhelpful.
 Also, as you know, cup size varies depending on him who makes the bra; therefore, discussing desired cup  size may also be inaccurate.






3.  Once you feel you have communicated your goals clearly,  allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals.  Again, in my practice, this decision is usually made during surgery.




I hope this (and the attached link) help.