Wide chest - 600cc or 800cc implants? (Photo)

Your picture shows asymmetry and uneven breast. The other concern is the position of the nipple/areola on your chest wall. Please seek another consultation and consider lift and smaller. 

Looking at photos online without an in-person exam makes it hard to give good advice on the right size of implant.  In general the implant width should correlate with the width of your chest and breast.  Choosing between a moderate profile versus a high profile is also related to your dimensions.  The 800 cc is quite large and perhaps would be needed but it depends on your measurements.  Rough estimation of cup size correlates with 200 cc of volume per cup size.  So at minimum you'd need 600 cc to increase from a B to the DD.  Start from there, my guess would be that you land between 600 and 800.  Your surgeon that's able to examine you in person would be the best to recommend.  Best wishes!

Unfortunately photos are not very helpful to determine the best size for you. Measurements and implant sizing during a consultation with a board certified plastic surgeon in your area is going to best answer your question.