My gf's favourite author is also PKD (she wants to know what your favourite so far is). She also raves about Cities in Flight by James Blish, Earth Abides by George R. Stewart, and the various stories of Cordwainer Smith. I say read The Chronicles of Morgaine by C.J. Cherryh, Saga of the Exiles by Julian May and Dancers at the End of Time by Michael Moorcock (those have more fantastic elements along with the SF, whereas my gf's recommendations are more hard-sf).

Oh, and Dune. You have read Dune, right?