Errikos, just one more thing that I think you should consider. Sibelius is pretty much dead, so I wouldn't make any life changing decisions until Steinberg's new notation software comes out. I think that people will be leaving Sibelius is droves so if you chose to go down this route, you would be in good company. If the application turns out the way I expect it to, there will be lots of tie-ins with Cubase and Nuendo, so for your purposes (and mine, TBH) it would make sense to have a sequencer that works well with your notation application.
DG