must-have SF authors beginning with "A"

I am beginning a project of organizing my library and deciding what
books to keep and what books I want to add.  I am working my way
through things methodically, beginning with the science fiction
section and authors beginning with "A".  Here are my thoughts so far ...

Adams, Douglas -- there is a single-volume omnibus (is that redundant?)
with his collected works.  that would be a nice readers' copy to own.
Adams certainly had a huge influence on the history of SF ... but not
one of my personal favorites.  Does it need to be in my collection? I
can always get it from the library.

Anderson, Poul -- I have a volume of collected stories.  What I would
like to have: a first of Tau Zero and (maybe) a complete run of the
Flandry and van Rijn series.

Anthony, Piers -- I'll deal with his fantasy in a separate section.  In
the meantime, there is an argument to be made for Macroscope.

Asimov, Isaac -- the first unqualified "must" in this section.  I want
the best possible editions of all the Foundation books.  The Robot
books are a lower priority.  The End of Eternity might be higher than
the Robot books.

Who else am I missing?