I have a few specific soundtrack artists that I have successfully listened to for inspiration, and I'd be happy to share my knowledge. I certainly hope this helps!
Two Steps From Hell. They create some truly epic orchestral pieces, almost always employing (non-distracting) choirs. Very good for fantasy, but this sort of music could fit anything. I specifically recommend Archangel, Call To Arms, Dark Ages, Am I Not Human, Freedom Fighters, Skyworld, Starvation and Protectors of the Earth.
X-Ray Dog. A slightly more techno sort of feel. Good songs are Dark Empire, Dethroned, Here Comes The King, Final Hour and Wicked Things.
Future World Music: Similar to Two Steps From Hell. Good for fantasy, though could be good for sci-fi. Try Welcome To My Fantasy, Gods and Demons, Dream Chasers, New Beginnings and Final Judgement.
Erik Ekholm. Not so heavy on the vocals, but still very awesome. Probably the best choice for sci-fi, but could very easily fit fantasy and other genres. I suggest Dark Energy (Epic Vocal Remix), Digital Warrior, Magnum Opus, You Will Never Break Me and Crusader of Glory.
Some similar and noteworthy artists include Clint Mansell, Hans Zimmer, Immediate Music, Audiomachine, Midnight Syndicate, E.S. Posthumous and Globus.
The band Pendulum is more mainstream and generally includes recognisable lyrics, but I find their music non-distracting or otherwise highly inspirational - especially for sci-fi or more surreal subject matters.