If you like Bartok's string quartets (I love them all) you may even like
those by Janacek, Enescu, Martinu,
** martinu was a great composer in my book. he did a lot, so some of his stuff is spotty, but it's really good in general. (for that matter mssr. beethoven did some crap too.)
many people neglect hindemith, but he could really write.
stig