kk, I recently did just what you are talking about, also at my wife's request. We rented a car in Barcelona and drove to Narbonne, Carcasson, and Foix. It was not that far and was well worth it! Despite what you may have heard about France, those cities were friendly and very interesting. As I recall, Narbonne was fairly close (2 hours) and there was a good interstate type road most of the way. There is a great cathedral in Narbonne.
There was a great medieval village called Mirepoix, not too far from Foix that was outstanding. That area of France is famous for the Cathars. They were a persecuted religious sect from the middle ages that built lots of castles. My wife really went wild over the shops and culture of Foix. I prefer Spain but must admit that I enjoyed that part of France. I have more info if you want it, including maps that I would gladly send you. I don't recommend Andorra, unless you enjoy outlet shopping and diesel fumes!
We visited Perpignan but frankly, it was not our favorite. It was sort of dull.