Since you are interested in Kullervo Symphony Op 7, here is a list of other items that you may find interesting.
Piano Quintets and Melodramas
Jaakko Kuusisto, Laura Vikman (violins) Anna Kreetta Gribajcevic (viola) Joel Laakso (cello) Folke Grasbeck (piano) Monica Groop (mezzo-soprano )
[ BIS / CD - released 1/Mar/2007 ]
Apart from Voces intimae, his final string quartet, the chamber music of Jean Sibelius has been rather over-shadowed by the orchestral masterpieces.
Complete Piano Trios (Volume 1)
Jaakko Kuusisto (violin) Satu Vanska (violin) Marko Ylanen (cello) Folke Grasbeck (piano)
[ BIS / CD - released 1/Aug/2003 ]
"Sibelians can rest assured that these are affectionate, deft performances, ideally recorded. BIS’s booklet is a model of its kind." (Gramophone)