If you hadn't put fast in there, I'd say just go for the Monk and enjoy the extra $$ in your pockets. However, Asura will keep up with fast music better than Monk - especially in the bass department. No doubt, Monk is an awesome earbud, especially for the price, but I think you'll enjoy Asura more for the music you enjoy.
An anecdote: My twenty-something son listens to a lot of hard bop jazz, and just loved the Monk. He chose it over much, much more expensive earbuds and IEM. He used to play jazz trombone in high school and said Monk's presentation reminded him of that small jazz club experience - intimate, smooth. Please correct me if I'm wrong, but I don't think that's what you're after.