Is 495cc too big on me in your opinion? 5'7, weight 120, and a 32A. (Photos)

As you can see, online consultants will not be of much specific help to you. My "best opinion" (this is based on limited information and should not be given too much weight in your decision-making": 495 cc does seem to be somewhat large given your anatomic starting point.   My best advice: further communication with your plastic surgeon.  It is definitely worth spending more time (prior to the date of surgery) with your plastic surgeon to discuss further.  As you know, it will be important for many reasons, that you feel comfortable that you and your plastic surgeon are on the "same page" prior to proceeding. Another piece of advice I give to of my patients: do not select breast implants that are any larger than necessary to end up with an outcome that you are pleased with.   In my opinion, "bigger is not necessarily better" when it comes to avoidance of complications and longevity of the breast augmentation procedure.
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, in bra sizers, and computer imaging) as well as careful measurements (dimensional planning) 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. For example, I have found that the use of words such as “natural” or "C or D cup” or "proportionate" 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.
  Best wishes for an outcome that you will be very pleased with.

Thank you for your photograph and questions.  The best way to determine size is to meet with your plastic surgeon and try on implants which you have indicated that you have done.  An in-person visit and consultation is your most valuable resource in arriving at a size that is right for you.  Best of luck.

Thank you for your question. "Tissue based planning" relies on your chest and breast measurements and is the safest way to ensure good long term results. Your surgeon should determine what size and projection are necessary to give you your desired result based on your body's measurements. The best way to assess and give true advice would be an in-person exam. Please see a board-certified plastic surgeon that specializes in aesthetic breast surgery. Hope this helps and good luck with your surgery.