This is my situation also. I already own the full SE with the plus extension.So, I have some decent brass covered with this.
Well, I cannot give you a definitive answer about the usefulness of dimension brass in your music. The concept looks very good.
For now, I just ordered brass 1 because of the multitude of articulations. At the moment, I am studying a couple of scores by John Williams. The brass writing there is so advanced. Very virtuosic, often dominating the whole orchestra.
So, I guess for anything that comes close to such a brass style the older brass 1 would be still better because it has such a huge variety of articulations.
But there are other styles were brass is not nearly as dominant. Here, you might get faster results with dimension brass. Hopefully, they wil melt better in an organic way.
Keep in mind that brass 1 is not a complete brass library. You are still missing bass trombone/contrabass trombone and contrabass tuba.
I guess that I can live easily with those low brass instruments having only a dozen of articulations.So,my SE would cover this easily.
This may be of not much help for you. Just the way I see things....[:)]