By SCOTT CANTRELL DALLAS -- If you've questioned whether the Dallas Opera really needed the new Winspear Opera House, check out the current production of Così fan tutte. In Mozart's opera, so much about nuances of singing and playing, you'll hear delicacies and details that wouldn't have gotten past the first three rows of the vast Music Hall at Fair Park.At the Winspear, recitatives have all the inflections of real-life speech.