Leopoldo Miguez was a prominent Brazilian Romantic composer whose style is heavily influenced by Liszt and Chopin. This work exhibits high virtuosity and deep emotional intensity.
The technical demand involves handling the wide-span chords and the intense, continuous octave work.
Comparable difficulty and character — good candidates for what to learn next.
Allegro appassionato (Op.11) is rated Henle level 7 of 9 — late advanced repertoire, roughly ABRSM grade 8 and above. In the RCM system it corresponds to about level 9.
You should be comfortable at Henle level 7 — meaning you can already play level 6–7 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of Allegro appassionato (Op.11) lasts about 6 minutes.
Allegro appassionato (Op.11) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.
Pieces at a comparable difficulty and character include Ballade No.2 by Franz Liszt, Bach- Toccata and Fugue in D Minor (Transcription) by Louis Brassin, Piano Sonata No. 23 'Appassionata' by Ludwig van Beethoven — see the full similar-pieces list on this page.