The main building - The Concert Hall holds around 2,000. The Joan Sutherland Theatre about 1,500, Drama Theatre 540, Playhouse 400, Studio 300 and Utzon Room 200. Then there is the outdoor forecourt which can hold up to about 10,000.
I have seen Gurrumul in 2008 and Paul Kelly I think in 2009, play in the Studio. It's a bloody intimate set up. Gurrumul played the Concert Hall in 2013 at the Vivid Festival
Not sure if the show Bruce puts on at Broadway would be as intimate in The Concert Hall or The Joan Sutherland Theatre. The Studio would be ******* amazing but probably cost $1,000. Probably worth it. But it would be fun if he did 5 shows a week for 10 weeks at the Opera House.
You might like these 2 songs that were on either side of Rosalita on the B side of his 2nd album in 1973, The Wild, The Innocent and The E Street Shuffle. (B side has 3 songs and about 25 minutes). These were recorded in Oz shows in 2013 and 2014 respectively, by TheAussiemusicanman who goes to music gigs and films 2 or 3 songs per show. He has 100's of videos on music.
Someone has taken the audio of Bruce on Broadway of Growin' Up with the Into - and layer over lots of photos of fans attending and of Bruce at the theatre sometimes with fans sometimes by himself and a very small bits of video vision from his performance. Its worth looking at some of the photos.