Top notch Prokofiev
The greatest set of piano sonatas of the 20th century are those of Prokofiev (in 2nd place, I would vote for Hindemith). The numbering is slightly confusing, as sonatas 1, 3, and 4 are works from his youth, while numbers 2, 5 - 9 are his mature works (and all masterpieces). As a complete set of the sonatas, the Boris Berman is highly recommended. Another good option on e-music is Bernd Glemser on Naxos. I prefer these two pianists to those of Frederic Chiu on Harmonia Mundi, who underplays the percussive side of the music. I agree with the previous review on the inanity of eMusics new download policy. But unfortunately it is, what it is. However, in this case, you can cherry pick individual sonatas, except for the 8th.