Hi,
I actually have a KN7, and I tend to think the sd card & audio capabilties has been a much overlooked feature.

I've recorded backing tracks as wav files from 9000pro, va7, a friends Wersi, and also planning to incorporate audio loops from Acid Pro.
I've then converted these wav files into mp3's & saved them to sd card via Panasonic SD Audio Writing Kit. From there I just plug the sd card into KN7 and play along using KN7 voices for left & right hand and the backing track is played as mp3 . Beats trying to revoice a midifile created on another instrument.

I haven't tried it yet, but the kn7 sequencer can sync with the audio tracks.

best wishes
Rikki