My favorite orchestral piece is Beethoven's 7th symphony. You should also look into Mahler's and Sibelius's symphonies as well. Sibelius's first symphony is a really interesting piece and is one of my favorites.
As for interpretations you can't really go wrong with Karajan, Bernstein, Furtwangler, or Toscanini. I'm not really particular about my conductors. I'm more critical of the interpretation by the pianist (but that's probably just because I play the piano).
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