Some classical collections you can get are pretty good but you'd definitely be better off finding a larger one because a lot of the small ones just have good but cliche tracks on them. Check out some Johann Strauss, particularly the very well known An Der Schönen Blauen Donau Waltz. Some of my favorite classical pieces are Camille Saint-Saens' Danse Macabre, Beethoven's 9th Symphony, Tchaikovsky's violin concerto, the Brahms piano quintet, Prokofiev's 1st symphony and 3rd piano concerto, Chopin's 1st and 2nd Piano Concerto, Rachmaninov's 3rd piano concerto, Schubert's String Quartet no. 14 (which he wrote while dying from syphilis from mackin on too many austrian babes). If you want some straight up oldschool go to the man who (literally) wrote the book on music, Johann Sebastian Bach and his once controversial Brandenburg Concertos which are considered some of the greatest musical compositions of all time
Some of that stuff isn't as chill as mozart but what it lacks in chillness it more than makes up in epicness. Romantic period classical is where its at though if you want some serious depth. The dynamics are far beyond just about anything written today, with the music portraying emotions over time much in the same way that our own feelings change and grow. Keep in mind that the character and interpretation of a piece is heavily influenced by the performer so i recommend finding other versions of things you like or if you want to hear them at a different tempo or something.