It's quite expensive, and I don't own it, but I have heard many great things about vir2's MOJO Horns.  (  http://www.vir2.com/instruments/mojo-horn-section  )  Apparently it is THE brass authority.

I actually like Studio Inst. Strings quite well.  Komplete is a great addition for all kinds of sounds, especially soundtracky stuff, as well as the Kontact sampler that comes with it, and that's where's you'd find the better brass sounds I think. 

Maybe due to budget a bit, I find myself leaning on my Motif XF a lot for natural sounds such as brass and strings.  Seems to work.
Keep us informed of your luck with whatever you purchase!