Answering my question (about the first piano sonata!) of ages past, Carus
has come out with a score in their Rheinberger complete edition containing
all 4 Rheinberger piano sonatas:  the "symphonische" sonata no.  1 in C,
sonata no.  2 in D-flat, sonata no.  3 in E-flat, and the Romantic sonata
no.  4 in f# minor.  (All but the first are recorded, and perhaps even the
first- I don't know.  I have only heard the second and fourth, however.)

Really, .really. fine, melodic, dramatic, Romantic (in all the good ways)
composer, if you don't know his music (and, of course, if you do).  His
organ music is fairly well-known as these things go, but his chamber music
deserves much more exposure than it's got.  Between Carus-Verlag and some
recent efforts by other publishers too (like Amadeus in Switzerland, which
recently published the 2nd string quartet, a fine recording of which
wonderful piece is on Thorofon- such a memorable, skipping opening, and
what comes after it!) this may just happen.  Good.

-Eric Schissel