I'm looking for a hotel in Barca for March.
Preferably 3 or 4 star, central and as cheap as possible.

MM - Yes I have done a search :p

Notyor have you looked into the Bancotel system. I looked and there were many 3,4, and 5 stars hotels for Barcelona in the Bancotel system. Depending on your travel dates you may be fortunate in finding a wonderful 3 or 4 star for 49.50 Euros.
Saludos,
Booklady

I would highly recommend Hotel Continental La Rambla. Great hotel, great location and great prices. You can get rooms that actually face La Rambla which are slightly more expensive and perhaps a bit noisier. Buffet breakfast is included. Visit their website at

http://www.hotelcontinental.com/home_ramblas.htm

The Hotel Continental La Rambla is a GREAT hotel that is close to everything and doesn't cost a great deal. Three nights twin room cost $234 with the tax and all. The breakfast is great and they keep the breakfast room open all day if you want to use the space for lunch or coffee during the day. Some of the rooms are quite small but who needs a big room. If you want a big room stay home. If you would like a little more space get a twin room instead of a double, more space but slightly more cost. Remember this is on the Rambla so some of the rooms are noisy. Ask for a quiet room, ask for an interior room.
I wrote and asked them if we could leave our bags at the hotel since we arrived before checkin. They not only said yes, they said come for breakfast and then go see the sights until your room is ready. This was an extra breakfast and they would not accept payment for it. I would stay again in a minute. We were there in July 2002