Revision from 350cc to 450cc or 500cc?

Dear Lacey,    50 cc difference in breasts volume is significant  The amount of cup size increase vary according to your chest circumference measurement in inches. For 32 - close to 1/2 cup  size, for 34 -  1/3 cup size and 36 - 1/4 cup size. Having that information , you will have to decide about your level of comfort with the cup size increase and your breasts cup size goal.   Always, consult with experienced board certified plastic surgeons who operate in accredited surgery center for your safety. Most importantly, check the before and after pictures of redo breasts augmentation  in the photo gallery, to make sure that they are numerous, consistent and attractive with nice cleavage, perky, symmetrical and natural looking.                      Best of luck,                                            Dr Widder

You
have not told us your bra size or provided photographs.  Simply adding volume may not achieve your
desired results.  If you want shape
change, a lift would be a better procedure. 
The technique I recommend is The Bellesoma Method.  Your breast tissue is reshaped creating upper
pole fullness, elevated higher on the chest wall and more medial to increase
your cleavage.  Vertical scars are
avoided, nipple sensation and the ability to breast feed are maintained, if not
injured from your previous surgery.Best Wishes,Gary Horndeski, M.D. 

Yes, it is likely that you will see a significant difference with about 100-150 cc increase in breast implant volume.   Likewise, the difference of 50 cc in volume does create a noticeable difference for most patients.***The much more important question with be: which breast implant (volume and profile) will be the correct choice when it comes to  achieving your desired outcome when it comes to breast size/shape/symmetry…?  Online consultants will not be of much specific help to you in this regard.
Generally speaking, the best online advice I can give to ladies who are considering revisionary 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” or "much difference" etc means different things to different people and therefore prove unhelpful.
 Also, as you know, cup size varies depending on  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 ( after the use of temporary intraoperative sizers).  Viewing the patient's chest wall in the upright and supine positions, with temporary sizes in place, help select  the best breast implant size/profile for the specific patient.
 Best wishes.