@grassonfly: I've listened to classical music since I was a kid (used to play double bass in various school and community orchestras). If you like Beethoven's Moonlight Sonata, try some concertos w/ orchestral accompaniment. You might like:
Rachmaninov's Piano Concerto #2
JS Bach's Concerto for 2 Violins, Strings, and Continuo in D minor (Double Concerto)
Brahms' Concerto for Violin in D Major
Tchaikovsky's Concerto for Violin in E Minor
R.Strauss' Horn Concerto #1 (w/ Barry Tuckwell or Dennis Brain if you can find one of their recordings)
Some other cool pieces (IMHO):
Beethoven's Symphonies #5 and #9
Mahler's Symphonies #1, #2, and #5
Mozart Symphonies #35 and #40
Rachmaninov's Rhapsody on a Theme by Paganini
Rachmaninov's Symphonic Dances
Shostakovich's Symphony #5
and adding choir to the symphonic repertoire:
JS Bach's Magnificat
Brahms' German Requiem
Mozart's Mass in C minor
Mozart's Requiem in D minor