Of course the big malls have the big department stores, which have big selections.
The best places to find unusual and discontinued fragrances are here too.
If you don't mind looking for a needle in a haystack, get over to Harry Hines just off the freeway. There are a dozen fragrance stores amongst stores selling jewelry and Korean restaurants. I've found some gems there, but no "niche" stuff there. The prices are excellent--especially if you are willing to haggle.
In Fort Worth there is a store called Parfumelle (parfumelle.com) that has an incredible selection, and the owner is a true lover and connoisseur of fragrance. The prices aren't the bargains of Harry Hines but they are pretty reasonable.