"Acting isn't nice," says theater innovator Anna Deavere Smith, acknowledging the naked edges that cut the heart when a performance uncovers complex truths. OK, it's not nice. But sometimes it's quite palatable nonetheless. Especially when the people doing it are as talented and in sync as the troupers comprising the New Theatre's double bill Don Juan in Hell and A Christmas Carol. Under the direction of Rafael de Acha, this foursome -- Bill Yule, Bill Hindman, David Alt, and Lisa Morgan -- turned themselves into the Devil, Scrooge, Don Juan, and a number of supporting characters, including a panting dog and a bevy of thieves. In these two script-in-hand productions, props, costumes, and scenery hardly existed. They weren't missed. The magnificent quartet demonstrated the power that the actor alone exerts on our imagination. And multiplied it to the power of four.