I stayed at the Atlantis Hotel and I found it excellent! Very clean, cosy and central! You have everything at you fingertips: shops, metro, airport-bus, sightseeing bus, the famous Ramblas.
The breakfast is really rich and the price is not so high! Our room overlooked the congested street of Career de Pelai. Nevertheless, the windows were soundproof and it didn't affect our sleep. Absolutely recommended!