Interesting question,we should ask some engineer or expert.
Classical Music (especially Chamber Music) need places like Theatre or Auditorium,because,if i am not wrong, the amplification comes only from the musical instruments.
It is important that the room where there is the Orchestra must amplify the sound of musical instruments. . . .so i do not know in places like 02Arena.
Mybe there are new technologies that permit a good listening to music played by an Orchestra.
I think Peter will think to all,he LOVES Music

p.s. Windspinner you have a very nice avatar!

p.s.2 i hope to have write clear,hey!! it is difficult. . . :-]