The server and dsp are two completely different things.
You cannot send 2 streams to the same server, however what you could do i suppose, is to use different broadcasting platforms.
You would still want to connect through shoutcast so i dont think that would work at all.
The server can only handle one stream at a time from the dsp. As stated as i understand it, you cannot make than one stream at a time.
You can have as many bandwidth selections as you want, dependant on the dsp theorectically.
If you want to cue music, then you need to get a program that will cue them up for you, unless you do this manually. ...i am not the expert here, but read the forums for what your looking for, you should find something similar, and the answer should lie between the two.
Hope this helps.