I found many great stores in Eixample. Many of the better art galleries are centered around Consell de Cent.
Gomez Turu Gallery, Consell de Cent 325: The gallery was featuring works of Salvador Dali when I was in Barcelona.
Manuel Barbie Galeria de Arte, Consell de Cent 321: I could have bought at least 3 pieces of works by Calder, Juan Gris and Picasso! A great gallery to explore.
Tea Shop Montcada, Placeta de Montcada 10 (across from the Picasso Museum): I found a great selection of imported teas.