I think you first need to mix it better, there is some clutter (lots going on at the same time) so you’d want to bring down the volume on some instruments that is not the brass lead. Second is stereo placement, you got the piano, staccato string, brass and pretty much everything in the center. You can use something like this to help you pan it; https://www.google.se/search?q=orchestral+position&sa=X&espv=2&biw=1920&bih=1094&tbm=isch&tbo=u&source=univ&ved=0ahUKEwjV0Mj60KfPAhXpDpoKHeuqA5QQsAQIGw
Personally, I think the brass samples sounds OK but it’s one of those that you really need to put in the correct room (reverb) to make it work. Try a convolution reverb with impulse responses from concert halls. Also use that reverb for everything to make it all it in the same acoustic space.
I think the master sounds OK, just focus on the mix.