I also meant to add that because of the way it sounds, it's more likely to be written by Romantic composers (e.g., Tchaikovsky, etc), than by the real classical composers (e.g., Mozart, Hayden, Bach, etc.). I suggest looking through
this site; go through Tchaikovsky's stuff, focusing on overtures, symphonies, and pieces with specific names, then trough his Romantic contemporaries. If that doesn't help, look trough Verdi, Beethoven, Puccini...Sibelius...Brahms, Bruch, and especially Mussorgsky, Grieg and Rimski-Korsakov (these last three's styles in some pieces are similar to the one you're looking for). I know it's a huge list to go through, but that's what I would do if no-one knew what it was.
So, to summarize, search for symphonies, overtures and pieces with specific names by Tchaikovsky, Grieg, Bruch, Rimski-Korsakov, Mussorgsky and then through their contemporaries...That's how I would start. Good luck, and let us know what you find!
Also, it could very well be a movie piece (it has that epic feel), in which case you'll have an even harder time trying to find out what it is. It isn't from Star Wars, though - that's for sure.