Antoni Stolpe was a brilliant but short-lived Polish composer whose piano music is heavily influenced by the virtuoso tradition of the mid-19th century. This piece is technically demanding and harmonically dense.
Master the stamina required for the driving octave passages throughout the piece.
Comparable difficulty and character — good candidates for what to learn next.
Allegro appassionato in C minor 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 10.
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 in C minor lasts about 5 minutes.
Allegro appassionato in C minor 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 Wanderer Fantasy in C major by Franz Schubert, Belfagor by Ottorino Respighi, Rhapsodie espagnole by Franz Liszt — see the full similar-pieces list on this page.