Fran, I have just downloaded a demo of Mixcraft 5 and it does look pretty good.
Have you tried using a software based vocal harmonizer such as Antares or MuVoice, etc.? How well does it work?
I haven't been successful in attaching a VST Instrument, e.g., Kontakt, etc. other than those which come with Mixcraft. It sees all the VST effects on my C: Drive but not the instruments.
Would you really need something as complex as Mixcraft when you already have Sonar X1? To me forte looks more like just a rack to mount instruments and effects. What is your assessment on this?