When swimming in the ocean of the classical repertoire it is impossible to drown. (Well, maybe avoid Wagner's Rhine and Valkyres at first, but, eventually, they will snare you!)
You seem to be residing at the moment in the Classical pond with Herrs Haydn, Beethoven, Mozart, etc. By the way, Haydn does have 104 symphonies and many string quartets. It is now possible to hear this music in recordings employing "original instruments" of the time as well as more modern interprations using standard instruments. So, there alone, you have a large chunk of sea.
Maybe to give yourself a bit of variety, swim on over to the late-Romantic epoch and hear some of the great, overtly-emotional orchestral works by Richard Strauss, Rachmaninov, Sibelius, and Mahler.
About buying CDs, search for a good used-CD store close to your home. Don't limit yourself to any labels. Read up on classical performers and their work. Two magazines I would recommend are "Fanfare" and the British publication, "Gramophone". Don't take all their reviews at face value but there are some good smart recommendations to be had.
Forgive the "water" theme of this missive but I've been listening to various recordings of Debussy's "La Mer" recently and may be just too wet for my own good.
With best regards.
