I can see that you are planning to get some designer sunglasses, anyway, there are hundreds of brands that produce and sell sunglasses for women and it could be quite hard for you to choose from the list. Anyway, it seems to me that in 2012, Karen Walker could be a hot brand because recently they have designed a lot of good sunglasses for women and they have always been specialized in producing sunglasses for females. Try to take a look at it.
for top brand designer glasses ,I think Gucci ,Dolce&Gabanna, Channel ,Dior,Linda and Victoria are all nice but much expensive . Usually they are more than $300 other brands like Ray-ban , which I think are the most worth-while . They usually comes around $150 .