Hi Many,
I believe you can use Jamstix to output MIDI performance data to Kontakt 3... which would play Jet-City. :-)
FWIW, Once we defined the feature set for Jet-City, Kontakt 3 was our only real choice for a sample playback engine.
Kontakt 3 is the only VSTi that can deliver necessary disk-streaming performance... while also allowing a great deal of customization (via scripts and skins).
To get an idea of the scope:
When a full Jet-City drum kit is loaded, there are 60 active channels (mics) that are routed/collapsed down to a more sensible 22 individual output channels. IOW, You have a full acoustic drum-kit mic'd with 22 separate mics. This allows you to choose from multiple close mics on each drum (along with separate overheads and room mics). All mics are in phase so you can mix/match without degrading the sound.
Technically, you can route all 60 channels (mics) to individual Kontakt outputs (using two instances of Kontakt), but that's not a real-world model/scenario.

Streaming multi-channel 24Bit/96k Wave files for each drum hit is a substantial load.
Thankfully, Sonar 8.31's low-latency performance is incredibly good when loading Jet-City into Kontakt.
With a fast well-configured DAW, you can set your audio interface to a 128-sample ASIO buffer size @ 96k (which is super tight timing wise) and play the samples in realtime from a set of Vdrums... totally glitch free. The samples all streaming from a single perpendicular-II HD (32MB cache)...
IOW, If you have 64 notes of polyphony sounding at any one moment, Jet-City is streaming 8 channels of 24Bit/96k audio for each of those 64 notes (512 channels of 24Bit/96k audio streaming at that moment).
When your done tracking the MIDI parts, freeze the Jet-City tracks... and what you have is essentially 22 tracks (mics) of well- recorded acoustic drums. With all the mic options, you can create a lot of different sounds from a single kit... without having to load lots of different samples to find the best fit. Simply mute/un-mute the various mics... and mix them to taste.
These are the reasons why we developed the library for Kontakt 3.