Here's Nick's as an example.
Solo BGM: Pulsar https://www.youtube.com/watch?v=CQHbZmPu-HI&feature=related
Boss Battle (Vs. The Reaper all others unconscious): X https://www.youtube.com/watch?v=IKRfPyFT0_0&feature=related
Boss Battle (Vs. Tenkei) (couldn't help it ^_^):Ad Suprema https://www.youtube.com/watch?v=ydpP75mvLSM&feature=related
Boss Battle (As SEES enemy): The Pretender https://www.youtube.com/watch?v=hUboRn-NKxI&feature=related
Victory Theme: New Heights https://www.youtube.com/watch?v=kFWaQgwWDuE&feature=related