What size should I choose? 415CC? 465CC? or 515? I am presently a 34/36A would like to be a DD or DDD.

Thank you for the question.  There is no accurate/reliable/predictable correlation between size/profile breast implant utilized and cup size achieved. Make sure that you read about the pros/cons associated with the different options for breast implant positioning; this website is a good resource in this regard. Despite your good description of goals, online consultants will not be able to provide you with specific enough advice to be truly helpful. Ultimately, careful communication of your goals (in my practice I prefer the use of goal pictures, direct examination/communication in front of a full-length mirror, and computer imaging)  will be critical.
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 are 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 "D or DD 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.  Again, the use of computer imaging has been very helpful during the communication process, in our practice.
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,  after the use of temporary intraoperative sizers.
I hope this (and the attached link, dedicated to larger breast  augmentation surgery concerns) helps.

Starting atan A cup breast it will be very difficult to achieve a double D or triple D sized breast.  As a general rule 200 cc of breast implant should increase you by 1 cup size therefore to go from an A cup to a double D cup is going to require more than 600 cc of breast implant.Your chances of complications go up significantly when you try to expand the breast so much especially over 500 cc.   The risk of capsular contracture and distortion of your breast is much greater when you place such a large implant under the breast instead of under the muscle.If you trust your plastic surgeons it is always best to follow their advice.  I would recommend you not focus on cup size but focus on the look that you want to achieve by using a breast implant sizing system evaluation.  During this exam implants of various sizes will be placed into a non-padded bra so you can see how you will look with each size.  For more information on choosing breast implant size please read the following link: