A friend of mine is sure I'd love it. But guess what, I never gave it a shot

Do recommend!
I see. I figured that when I read Wagner's Die Walküre in your list, you were an Opera fan. Seattle Opera used to put on the entire 4 part Ring Cycle every 4 years. I spent a couple weekends down there in 2013 seeing it. Amazing stuff. I think San Francisco Opera is staging it this coming summer, so I'm considering spending a week down there to see it again, and do some surfing on the Lost Coast, bouldering over in Tahoe, and another little tour of wine country.
If you like Wagner, check out the Ring Cycle and Tristan Und Isolde.
Others... I love:
Dvorak's
Rusalka
Rimsky-Korsakov's
The Legend of the Invisible City of Kitezh
Tchaikovsky's
Eugene Onegin
Berlioz's
La Damnation de Faust
Gluck's
Orfeo ed Euridice
DeBussy's
Pelléas et Mélisande
Offenbach's
Tales of Hoffmann
Monteverdi's
L'Orfeo
Purcell's
The Fairy Queen
Mozart's
Idomeneo
Oh and you may want to check out Janáček's
From the House of the Dead, given your love for Dostoevsky.
You may have heard this before from Tales of Hoffmann:
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