Sibleius is very much for writing the score, its excellent at plaiyng music back, and you can play music to it and it scores it out.
You can change dynamic markings if you want to put in solos...
*Note* This program is very different to Grarage Band, as it can't layer recordings. It just writes out the notation.
Heres an example of it:
However, as a Garage Band equivalent, Cubase is probably a better piece of software for you, as you can do multi layer recordings of both midi and audio, and move those round and mix em up
Example:
If you decide on Sibelius, any version would do, i have Sibelius 5, but it costs
a lot you may be able to get an earlier version (Sibelius 3) quite a bit cheaper, and they do basically the same thing