I think Stupid Dream came next. Anyway, their most recent stuff is a bit heavier and, to me, much better.
Yep, Stupid Dream was the next studio album after Signify. Coma Divine was the next album, but was a live recording. There are expanded two disc remastered versions of both Signify and Coma Divine available. Both are great. There's also a two disc remastered version of Sky Moves Sideways as well (got mine autographed at the PTree show in Stuttgart in November 03).
Also, if you like Signify, you might check out "Metanoia". It is a limited edition release of improvised instrumental music that they recorded during the Signify sessions. It's probably hard to find now, I'm guessing it's OOP.