The Oresteia is the theater itself. Mounted to inaugurate the Rep’s new 600-seat playhouse, Aeschylus’ ancient trilogy shows the spiffy space to glorious advantage. The huge stage, which can be seen with ease from any seat in the house, encompasses massive stone walls and temple columns beautifully. Someone might counsel the actors – especially in the second play, “The Libation Bearers” – to tone it down a little. (Declamation can turn to stridency very quickly). The wonderful acoustics can carry even a whisper to the farthest rows (which, thanks to the architects, are not all that far away)