Another thought . . .
Prior to playing "arranger keyboards" (about 5 years ago), I sang & played a standard electronic keyboard (mono output) in a live band. For this type of situation, stereo was not as important because the keyboard is only one instrument among the other musicians/singers on stage (natural surround stereo). Arranger keyboard performance is another matter as we are attempting thru one instrument, to emulate the entire band, thus stereo output is essential.
- Scott