Three things:
1) Laptoppop is correct, Vegas Audio is soon to be no more. The company is moving towards just putting out "Vegas", with all audio and video together (this from the Electronic Musician email updates last week)
2) I use Sonar 2, and don't have any problems with complexity. It is easier than Cakewalk Pro 9, and I agree with cominginsecond, that having MIDI makes it much more flexible in the future. After all, MIDI is pretty cool...
3) I've gotta echo ecs113's question: What is it about Cubase that is insufficient? If there's some fundamental problem there, it may change the advice you get on this board.
-mg