Funny, I was just researching this. I'm also looking for a more difficult Haydn Sonata so I went to the Audition requirements for Julliard to see what they would accept for a Haydn sonata (knowing they would only list the more difficult ones). The one's they listed were Hob 20, 23, 32, 46, 49, 50 and 52. I did the A flat a long time ago. I was thinking of resurrecting it, but I seem to be more drawn to the B minor this time. Good luck in choosing.....