I'm a great fan of Martin too. A few more:
Franz Berwald, a Swedish composer from the early Romantic period, e.g. his
piano concerto in D.
Walter Braunfels, writer of the best opera ever,
Die Vögel (bizarrely enough entirely online).
Ernest Chausson, French Late Romantic-ish, e.g.
Poème de l'amour et de la mer.
Niels Gade, a Danish Romantic composer
Giullaume Lekeu, a Belgian composer who died much too young:
String Quartet in G.
Bohuslav Martinů, born in Bohemia, somewhat modern, not unlike Martin, e.g. his
Sinfonietta.
Some obscure Austrian classical composer, a certain Mozart. He wrote e.g. a quite decent
Laudate Dominum.
Karol Szymanowski, Polish, modernish, e.g.
Stabat Mater.
Michael Torke, student of Philip Glass, I believe, but more interesting:
Telephone Book, but later works didn't really impress me that much.
Jan Dismas Zelenka, the Polish Baroque composer that even Bach admired, e.g. this
sonata in g ZWV 181, or the
Simphonia a 8, or
Miserere ZWV 57.
The honor position is reserved for a composer who is perhaps more limited in his expression, and who, like so many other composers, was simply at the wrong place at the wrong time, but who has written some of the most beautiful and heart-wrenching works I've ever heard: Gerald Finzi. Listen to his https://www.youtube.com/watch?v=EkQbzZgwfl0 (Eclogue for piano and strings) later on the evening when everything is quiet.