hi Steven,
GNS-MS01 uses Yamaha's proprietary connection which doesn't exist on any other subwoofer. The problem is not connector itself... it's about amplifier solution of GNS-MS01 system. In short:
L+R channels from keyboard go to subwoofer where signal is amplified. Inside subwoofer, there's a passive crossover circuit at the output of amplifier, which divides signal toward subwoofer speaker and toward L+R satellite speakers. That is, for L+R satellite, amplified mid/high frequency signal goes back to keyboard (that's why so many pins).
No studio subwoofer has such solution. That is, L+R output on subwoofer (for satellites) is never amplified, because L+R monitor speakers have their own amplifier built in.
That is, if you need different subwoofer, you need to buy monitor speakers as well.
Bogdan