I have 650cc hp silicone implants and switching to 800cc silicone. Will I be able to see a difference in the implants?

It will be a subtle difference.  Not significant.  The implant selection should be based on a combination of your desired size, soft tissue dynamics, breast base diameter and skin elasticity.  I recommend an in-office examination as well as a detailed discussion with a surgeon who you are comfortable with.   Finally, make sure your surgeon is a Double-Board Certified Plastic Surgeon certified by the American Board of Plastic Surgery (ABPS), a member of the American Society of Plastic Surgery (ASPS), a member of the American Society of Aesthetic Plastic Surgery (ASAPS), and a fellow of the American College of Surgeons (FACS).Best,Dr. DesaiBeverly Hills Institute for Aesthetic Plastic SurgeryHarvard Educated, Beverly Hills & Miami Beach TrainedDouble Board-Certified, Double Fellowship-Trained Beverly Hills Plastic Surgeon

As the previous Plastic Surgeon mentioned, there are a number of factors that will determine how this additional volume will look on your frame.  But without photos, there is really no way to tell you how much of a potential difference this will really make.  Also, having performed literally thousands of these cases I can personally tell you that silicone upsizing doesn't always look as dramatic as you may think even when you are going up by this much volume.  Instead, the results are often subtle.  One option to add even more volume is through fat grafting performed at the same time as the implant exchange.  The implant can be added below the muscle and the fat in the glandular/fatty tissue above.  Best to discuss your thoughts with your Plastic Surgeon and have him/her guide you through this process.  Most importantly, make sure that your physician really is a Plastic Surgeon.  In your area specifically, there are a number of "Cosmetic Surgeons" who will claim to perform Plastic Surgeon.  Best to choose a surgeon based on experience and actual training and not on price.  I hope that helps!Happy Holidays!-Gregory A Buford MD FACSBoard Certified Plastic Surgeon

Any time you add more volume to your breasts, especially given a fixed and stable volume with an implant, you should be able to tell a difference.  However, a lot of factors go into how much difference you will see, including your starting breast size with and without the implant, amount of native breast tissue, placement and shape of the implants and goal for volume increase.  Unfortunately, none of this can be accounted for online and requires an exam in person, so ultimately your best answers to these questions are going to come from the surgeon who is doing your implant exchange.  Since this will be at least your second breast surgery, for your best outcome, make sure you take the time to communicate your goals and desires to your plastic surgeon and make sure he or she understands and is on the same page.  Best of luck! 

Thank you for your question. When increasing the volume of your implants, you should be able to see a difference. This does depend on whether the same style implant is being used. Make sure you discuss this with your plastic surgeon prior to your surgery date. Good luck with your procedure. 

Thank you for the question. The upsizing of breast implants you are considering will likely make a noticeable difference; the MORE important question is whether it will make enough of a difference to achieve an outcome that you will be pleased with. This question cannot be answered online.
Keep in mind as you are thinking about your goals that sometimes adjustment of the breast implant pockets (capsule adjustments) may be necessary to achieve the outcome you are looking for.   
Generally speaking, the best online advice I can give to ladies who are considering revisionary breast augmentation surgery 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 "up a cup size” or "DD cup" 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 chosen plastic surgeon to work with you in determining the best plan to achieve your goals.
I hope this helps. Best wishes.