Well if you want avant garde, classical/electonic try Stockhausen, Ligeti, and Xenakis( i may have spelled this wrong) Ligeti did the music to 2001 a space oddyssey( not Strauss's waltzes of course).
As actual bands, Id say coil. They did the soundtrack for a movie as well- the angelic conversion( and i know they are a big influence for Ulver). Nurse with wound is pretty fucked up, but i dont think they hit that whole sparse sounscape.
Id love to hear some good recommendations too, because its damn hard to find music of this nature.