I've been meaning to bring this up for several weeks now, but I highly recommend Darren Korb's "acoustic frontier trip-hop" soundtrack for the video game Bastion as a stand-in soundtrack for an as yet unmade soundtrack for Avatar: The Legend of Korra. I had the Bastion soundtrack for several months when I first noticed the slight similarities between Bastion and the music on Korra during one of the last episodes of the show's first season. Take a listen to "Bynn The Breaker" and try picturing this playing as Korra and friends patrol Republic City.
Or maybe taking on some Equalist thugs during "Terminal March."
If those don't work for you, there are two vocals from the soundtrack, "Build That Wall (Zia's theme)" and "Mother, I'm Here (Zulf's theme)" that are really worth listening to several times. Late in the game, Korb combines the two into the beautiful and haunting "Setting Sail, Coming Home." Below is Korb (who was audio director on the game) and vocalist Ashley Barrett performing the track live. Enjoy.