I have got quite big boobs (albeit lopsided after wle!) and have tried all kinds of bras since the op. I struggle with underwires now as they don't seem to stay where I want them on the op side, so am opting for unwired and the most comfortable I have found is the "La Isla" range. They are not very expensive and you can get them from Amazon (with free returns if they don't fit) or new on Ebay. Even though they have very good coverage I find they are low enough at the side to avoid my lymph node scar. I also have lymphedema across my chest and find they are soft enough not to cause pain or make it worse.
I hope you find something that works for you.
I find that Anita bras are good - best one I have is 'Nastasja'. Sold as suitable for immediately after surgery and I found it was OK on scar and still my favourite as very comfortable (in fact I bought another one!). However it is expensive so best if you could try it (or any others) on before buying. I got mine from Nicola Jane - they have three shops so I went and tried on lots of bras and prostheses. Not sure how this one would work in larger sizes but they do have a wide range from different manufacturers and they were very helpful. If you are not near to one of their shops they say they can give 'phone advice but it could be quite hard to judge what would work with your scar. Most mx bras seem to come up quite high so you might need to try a few to get one that is right......