Hello, I've made a really intelligent statement, haven't I? I first didn't realize, that the values in the playback dictionary are only used, when there is no suitable Sound-ID available. The funny thing is, that I really thought, that I hear a difference, when I changed the values. I've tried it out again and didn't hear a difference any more, which is quite sad, because now I feel, that staccato is played to short especially at slow tempi all the time.
As a beginner - rather than an expert as you have perhaps noticed ... 
- I'm a bit frustrated. If I listen to the Demos and the Tutorials, everything sounds great, but if I listen to the playback of VSL and Sibelius, I'm not very impressed. That's probably my lack of understanding everything. The first thing I've learned is, that the dry sound on it's own is not enough. So I need some reverb. Now I've downloaded Vienna Suite as a trial version and looked at the videos and read the manual and got an overview, what is possible, but I can't transfer things to my needs. I really would like to spent money, but if I can't see a satisfying result with a reasonable amount of effort, there is no chance for me to do this.
Perhaps it's the kind of music I want to do: a brass quartet playing a romantic piece of music. The sound should be soft, but the trumpets (12S Trumpet C+ matrix from the Special Editon) are annoyingly aggressive, especially when playing forte and there are some notes, which stick out with no obvious reason. There are probably ways to change this, but I don't know where to look at and how to do this. For someone like me, some proper (beginner) examples would be more helpful than a whole bunch of possibilites.
Heiko