This piece has a LOT of potential. Listening to the tonal atmospheres you have going on, it reminds me a little of something that might come out of a Halo battle scene, with the choral samples. The strings could have used a bit of temperament - they are a little harsher in some areas than I would expect, and they don't have much of a varying volume. Still, good choice on the melodies and the different styles within the song. I would mess around with the velocity on the strings.
Truly, I enjoyed it, overall, and it would be a great addition to any tense scenario. Looking forward to listen to your other music. ^__^