Hey Ross, check out the E.Y.E: Divine Cybermycy soundtrack. These are great ambient tracks with a cool sci-fi theme.
It can be downloaded from the official site here:
http://eye.streumon-studio.com/index.php?page=music
The game is pretty great too. It's an FPS-RPG hybrid, it has some elements from Deus Ex and System Shock 2 and some great combat.
I also recommend these soundtracks:
Thief: The Dark Project
Thief II: The Metal Age
Hitman: Codename 47
Hitman: Silent Assassin
I'm thinking these can be procured by getting the GOG.com versions of the games.
