For anyone interested in putting a solo string library to the test:

Beethoven\'s string quartet op.130, 5th movement (\"Cavatina\"). Definitely one of the most moving and expressive quartets I\'ve ever heard. (well, that movement, anyway)

EDIT: if you haven\'t heard this and want to pick it up, pick up the performance by the Guarneri Quartet, on the Philips \"Digital Classics\" CD. Dunno if it\'s out of print or not. Classical pieces are always interpreted differently and played differently.. I\'ve actually heard some pretty disappointing performances of Barber\'s \"Adagio for Strings.\" Anyway, this recording is really nice.