The biggest bang for your buck will be Max Richter. He's got an epic catalogue of ambient piano music.
Angelo Badalamenti has some cool tracks in that genre.
also check Hans Zimmers work on The Ring,
check Third by Hiatus
Olafur Arnalds of course
Nils Frahm is amazing...
there's an awesome track by Sigur Ros on the Untitled album (I think untitled #3)
Then theres the soundtrack for American Beauty of course
and to top it off...listen to H.K. farewell by Placebo (thank me later)