Can someone recommend a convenient and classy hotel in Barcelona. I am booked into the Hotel Artz for the beginning of the trip, but will have to move for my final night because the Artz is full. I prefer something boutiquish, centrally located, either historic or modern, but definitely not corporate. Suggestions are greatly appreciated. Thank you. JC

The following hotels are all in your category and all are popular on this site, run a search:

Claris (derbyhotels.es)
Condes (condesdebarcelona.com)
Ritz (not the Arts, ritz-barcelona.com)
Majestic (hotelmajestic.es)

I would keep trying to extend your stay at the Arts, as moving for one day seems more trouble than it is worth.

I stayed at the Ritz last year and really liked it...very convenient, but might be bigger than you want, not boutique type place.

I stayed at the new Marina hotel which is on the end of the ferry dock, giving spectacular views over the city (as long as you don't mind the early ferry horns). This is a big hotel but the staff were very friendly, the rooms very well appointed, and a very convenient location without the constant traffic noise from the more central hotels.

The Claris will certainly fulfill your requirements: centrally located, although not boutiquish, historic building with sleekly designed interiors.

http://www.derbyhotels.es/hoteles/claris_ing.htm

I loved the Hotel Arts. I doubt they won't be able to extend your stay. I agree it is a shame to move for just one night.
But, the Hotel Artz is really a business hotel and is VERY corporate. It's location is not ideal either. You're going ot be getting taxis back and forth all the time. I would suggest you consider a hotel IN the city instead. If you are looking for classy, you are looking for the Ritz.