Ludwig van Beethoven declared in 1806 that another composer of his acquaintance was the greatest of any then living. Which of his contemporaries had impressed him so deeply?

Beethoven genuinely admired Cherubini's operatic and dramatic compositions, stating he considered him the greatest living composer. While Haydn was an important influence and mentor, he died in 1809, and the question specifically references Beethoven's 1806 declaration. Hummel was a contemporary but less revered by Beethoven, and Liszt was too young (born 1811) to have been the composer mentioned.