In STL, I notice a lot of Tiffany silver and Konstantino. Most engagement rings are from locally recognized jewelers, so lots of custom rings or settings like Tacori.
In Nashville, Tiffany is very popular. King Jewelers has brought some serious watches to town like Hubot and Patek Phillipe. Most designer jewelry you'll see in Nashville that is not Tiffany will be in the Vanderbilt area, where many East Coast transplants live.
In New Orleans, it's all about Migonne Faget and Adler's.
I see EVERYTHING in Chicago. Chicago has all of the big stores and even the department stores sell fine, fine jewelry. I notice lots of Cartier love bracelets and Yurman... But branded or not, I notice lots of large colored diamonds (or just large diamonds).