How much bigger would be best?

I'm 171cms tall, 61kg and I hate how pear-shaped I am. I only wear a 32C bra but my waist/hip measurements are 28 and 39 respectively. My legs are pretty slim but I hate that I look all hips and no boobs - despite carrying the tiniest bit of fat there and it all being down to a wide build. I'm a healthy weight but I feel I look totally disproportionate. I've always wanted to get surgery to make my breasts bigger but I don't want them to be unrealistic or give me back problems etc. If I were to eventually arrange something, just how big would it be realistic for me to go?