I had the KN1000 and it does have some very good sounds and it did sound good in mono.

The Yamaha PSR3000 and Tyros are a bit different, in that for the very best sound, you will want to play in stereo if using a standard PA. The PSR2000 and Tyros sounded very bad to me in mono.

I have heard that the Bose PAS will work ok in mono if you use voices that are not as good as the Live or Mellow Grand, and/or if you tweak the sounds. I have not heard it myself, so I am only stating what those Bose owners have said. But, then again that Bose system runs $2000 for mono.

Best
Scott