Replacing 235cc saline implants with silicone 350cc. Will this be enough to make a noticeable difference in size?

Dear L,   You did not provide your chest circumference measurement in inches which is critical for the correct implants' size selection. The difference of 115 cc  is a significant increase regardless of your chest size.  For 32 chest size it will be almost full cup size and for 34 it will be about 3/4 of a cup size.    In regard to changing from saline implants to silicone implants, I would like you to give it a second thought. The switch will cost you about $1000 more. It might force your surgeon to make the incision in the sub mammary crease which will be longer, visible and far from the cleavage area to give you a nice cleavage. Additionally, it is a myth that silicone implants are more natural than saline implant, since I replace many silicone implants with saline implants to the delight of my patients.   Always, choose the quality surgeon, rather than the implants' type. Check the before and after pictures in the photo gallery, to make sure that they are numerous, consistent and attractive with nice cleavage, perky, symmetrical and natural looking. Also, your surgeon should be ,only,  experienced board certified plastic surgeon who operate in accredited surgery center for your safety.                                  Best of luck,                                                   Dr Widder

Thank you for the question. 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, patients undergoing revisionary breast surgery should understand that there may be many variables besides breast implant volume that come into play when determining optimal  breast implant selection during revisionary breast surgery.   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. For example, I have found that the use of words such as “natural” or "C or D cup” or "noticeable difference" 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.  Personally, I find it most beneficial to have a wide range of breast implant types, sizes, and profiles available.
I hope this (and the attached link, dedicated to breast augmentation surgery concerns) helps. Best wishes for an outcome that you will be very pleased with.  

A rough estimate for you would be to add the volume difference in a baggy and stuff it into your bra to see.