You'll find nothing else by Orff that resembles O Fortuna. If you enjoy dark, huge choral pieces, there are many options though...
-Requiems by Mozart, Verdi, Brahms, Berlioz (usually the Dies Irae)
-Prokofiev's soundtrack for Alexander Nevsky, esp. "Battle on the Ice"
-Shostakovich's Babi Yar symphony (don't remember the number)
-Mahler's Das Lied von der Erde
-Anything by Wagner or Bruckner if you have the patience for it...
and finally
-end battle of Final Fantasy 7
All quite better quality than Orff, no offense.