Not quite, in this context it just means that the person has news to tell. The alternate meaning that you have provided can be used to show that you are impressed at something, although it doesn't quite mean 'very good'. You could say 'that's some car you've got there': this implies that you have an impressive car in the eyes of the speaker. That being said, if you said 'some' with quite a bit of emphasis you could alter the meaning. You would say something like 'I've got some news to tell you': this implies that the news is something important and somewhat 'impressive'. Hope I could help :)