I bet some of the ladies here that say they are 32DD 34DD might really be 30G. I know that sounds nuts. But I measure a 26DD, which nobody even manufactures, so I get the next best, 28D, which is very hard to find. For people that think this sounds crazy, a 28D has the same cup volume as a 32B on a much smaller band. So I'm not like a cartoon or anything, I'm just very petite and only very mildly busty.
Contrary to other posts here, I think VS is relative junk. They don't carry a good range of sizes, it's not really high quality stuff, you are basically paying for the name. I used to work Limited Brands (the parent co. of VS) and they just churn out mass market stuff with a "designer-for-the-everyperson" price tag. I'd skip them.
Anyway, I highly recommend you determine your correct band size (just measure around your ribcage) and buy accordingly. Bras wear out because they lose their stretch, and a tight new band is the most supportive. You should buy your bras so they fit very snugly on the loosest hooks, then as they age, move into the tighter hooks to compensate for loss of elasticity. If you buy a bra with a band that only supports on the tightest hooks, it isn't going to last very long.
I've had the most luck finding bras at specialty stores and at amazon, where some styles qualify for free shipping and returns. Because on top of having an hard to find size, I have "shallow" breasts- my breasts have a wide base and not a ton of projection- the don't really go out or down much, and a lot of my breast tissue is tight up against my chest, if that makes any sense. Cleo by panache is a great fit for me. They are pricier than department store bras, but they end up lasting longer.
Plus I like to treat my breasts to proper support, since they have been so good to me and my family. (two kids, 2.5 years apart, each nursed to age 3, so I tandem nursed for 6 months). They came out of 5.5 years of breast feeding looking as perky as they did at 19, I'm a wee bit proud of them, so I want to keep them lookin' nice.