I found a few actual demos of BK-5 that sounds interesting, also heard a few BK-7m with excellent sound. Once again, I´m following very close this keyboard...
BK-5 Audio Demos
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My german is worse than english, I used a translator but they seems to like it!!!

By the way,
i think this is a good alternative to the mini keyboard of Korg MicroArranger.
1.-There´s a lot of power (24w rms) (my Fp4 piano with 14w at half volume is enough for a room with 100 persons using backing tracks. Dinner, OK!)
2.- Is bigger, at least, seems more "pro" than a toy size keyboard... (my opinion)
3.- The keys are bigger. This one I can imagine are not a good keybed, no aftertouch, probably shorter than my Tyros4 keys, but bigger than accordeon keys.
For persons with big hands from years studying piano as myself, the accordeon keys is beyond the confort zone...
Just some thoughts, What do you think, People?

Jo