It's always a trade-off with these things Bax... or it seems so to me. PowerTracks Pro is a GREAT MIDI tool but I HATE the audio handling/editing capabilities. n-Track, Reaper etc... handle audio very gracefully but MIDI is usually not as graceful. So I keep more than one tool in the box.
The Roland Virtual Sound Canvas should work well in n-Track. The DXi version is usually much better than the VST version. The VST version introduces too much latency for my liking. The DXi as much quicker. They sound identical, so I use the DXi version in PTPro, Reaper etc and it works well. I can't remember, but I think I used the Roland DXi with n-Track a long time ago and it was fine.
MIDI? You just need to grok about with it. You'll get the hang of it.
I have that DXi thing show up (must have been from cakewalk) but I don't think I have the right VST like I do with the sf2's, I have DXi's option that show up, like dahornet and some things I may have gotten from Reason but they are more FX like warping, echo and such no actually "player" to play samples with.
In my case the VST is not so bad since I am only using it to do single midi tracks at a time to make them wav. files, except for the case of drums that are on various tracks, which is no bid deal because they all can be sent through the same VST to play from the same sf2 folder at the same time.
If DXi's use less latency tho, it would be good to have one that will play a sf2 file.....surfs up! time to google.....