I have Francois Couperin 12 CD "Pieces De Clavecin" to finish listening to that I'm halfway into (by the way why can't the 1001 book recommend a compilation CD or an individual suite or even an individual book to listen to instead of recommending me his entire keyboard output that takes 12 hours to listen to. It's a complete and utter chore to listen to)
Followed by Andre Ernest Modeste Gretry - Zemire et Amor opera.
After that it's Alfred Brendel 4CDs of Joseph Haydn Piano Sonatas which I assumed is the same as what you have.
I would probably complement listening to Brendel's piano sonatas with Ronald Brautigam period instrument recording of the same sonatas as well.
I have listened to all of Mozart's sonatas and all of them are good but only few of them stand out as Great such as the 8th piano sonata and the 14th. However they are due to a relisten as the 1001 book included EVERY SINGLE Mozart Piano Sonatas in the 1001 recommended recording (like I said why not pick individual highlights. If you are going to simply pick every single piano sonata from a composer. You might as well do that with Beethoven as well where his 32 piano sonatas are all essential. However with Beethoven they just picked individual highlights instead of recommending a single box set that has every piano work he has written). Again i'll probably register to it with a period instrument recording by Ronald Brautigam