The only Fall of the House of Usher I know of is the one by the Alan Parsons Project on the "I Robot" album. It has a section on classical guitar. Perhaps someone has made a guitar-solo arrangement from this work? Parts are quite lovely.

A search of peppermusic shows 2 pieces: one an opera by Philip Glass (ewww), and another an SATB choral work by Habash.

Sorry I couldn't be of more assistance. Good luck!

Alex
O..O
=o=