In my experience, it's not just the cup size, it's the waist size too. For example, Pamela Anderson's 36DD's in the pictures I've seen look a hell of a lot bigger than someone with, say, 32E or 30FF breasts. Likewise I've seen B/C cups that varied in size dramatically between them. So don't just go buy cup size. Let's just say that I've had girlfriends with breasts of all sizes and I don't have any real preference between them. Okay, maybe bigger than an A is okay, but so long as they don't look completely over the top or completely flat then I'm okay.
Also, clothes look better on girls with small boobs? Psh. Typical women. Try getting a girl with an A or B into a halter-thingy and then you'll see that small boobs mean little in the fashion world other than fulfilling gay men's fantasies of a woman's face on a boy's body.
To summarise: Waist size matters as much as cup size. Also, once you come down to it, to quote the great Adam Hills when speaking to women who worry too much about how guys view them - "Once you come down to it, we're not that picky."
