The Grieg Sonata is really cool. I played the first movement of it along with another set of exam rep I had prepared for RCM (the sonata movement was just for fun though). Ended up learning the rest of it for the next level exam. That is a really, really good piece, with a very effective finish (if you are in a resonant hall, the texture will fill up nicely). Grieg in general is underplayed... except for his Concerto, and like 2 of the lyric pieces.
So ya, check out the sonata, it's about 25 minutes long, about as difficult as the Tempest Sonata by Beethoven, maybe easier/harder in a few spots. The second movement, ahhhh so good.