Hi G_m,
I suspect it might be that many restaurants have a basis of Catalan cuisine, but then build upon it, that is certainly the case of some of the top chefs in Barcelona from Santi Santamaria out at Can Fabes, Ferran Adria in his spin off projects, (and his proteges like Jordi Vila at Alkimia, Carles Abellan at Projectes 24 and the guys at Santa Maria across the street), Carles Gaig, etc
Catalan cuisine shares a lot with Mediterranean cuisine, which it is obviously part of, so many dishes especially fish and seafood are the same. There are obviously some specifics, I haven't been but I understand Via Veneto, despite its name is pure Catalan cuisine, and that Ca l'Isidre is Catalan with French influence, at the simpler end there are places like La Llesca in Gracia, dedicated to pa amb tomate, local cheeses and sausages,or Pla de la Garsa in La Ribera and at any tiny local bar/restaurant you'll find the simple local dishes. When my friends lived in Gracia, the local Can across the street was good simple Catalan food, now they have moved the local restaurant for last minute, can't be bothered going far meals is good simple Basque food., I guess people choose these sort of places by proximity rather than ethnicity.
Frommers Guide used to have Catalan as one of its categories, but I see now it just has Spanish / Mediterranean, though it still has Catalan as a subcategory on the actual restaurant entries. It still has quite a nice introduction to Catalan cuisine
http://www.frommers.com/destinations/barcelona/0045010028.html
Its list of restaurants
http://www.frommers.com/destinations/barcelona/45_inddin.html
Some of its dining best bets are probably worth a try as well