tenfoot
lingyai
I've used midi-only VSTs like Cthulu and Catanya in X3e and in Hopkinton -- both work fine here. Have also used EZKeys and Kontakt in midi-out mode.
I use these as well but I think we are discussing different beasts. These are vst instruments that output midi notes. Vst midi plugins can be applied to a midi track in a similar manner to the mfx midi plugins that come with Sonar.
Ah, ok. In which case -- hoping I am now talking about the right thing -- I can say that Frankie's Midi plugins (free and rather useful) work fine here. After they're installed, you'll find them as a new group under Midi FX when you right click a clip. Great humanizer (helps if you are familiar with probability distributions to appreciate the GUI) and also something which will send each of the individual notes of a chord to different channels -- an easy way to get a individual instruments from string quartet to play your 4-note chord progressions, for example.