Martinu is superb, one of the underappreciated composers of the last century. I've heard a fair chunk of his works, and his symphonies and string quartets are outstanding. For the string quartets, the Panocha is the finest of the sets I've heard, though the Martinu Quartet is also excellent. (Even the Stamitz, my least preferred here, are really good.) The piano concertos are generally quite good. There's a complete cycle on Supraphon (naturally) with Emil Leichner, and the great Rudolf Firkusny recorded some as well. Firkusny is better here. The Cello Concertos are almost as good. The piano quintet on a Naxos release is outstanding, and the violin and piano works, particularly the later, non-study works offer some rewarding listens. For opera, I've only tried Julietta, and while not up to the standards of, say, Janacek, it is quite good. I cannot think of a bad Martinu piece.
On the symphony side, though you just got the Jarvi set (which I have not heard), the new Belohlávek set is absolutely top flight, besting even the Neumann set. There are ample options with this composer.
