Having owned the Stereo 100 and a Rogue Cronus Magnum-II, I would opt for the new CM-III and request the factory resistor and capacitor upgrades. Total expenditure would be very near that of a new ST-100 and you'll simplify your setup.
While I liked both amps, I found the CM-II had superior musicality - for whatever reason, it was simply more involving. Both lean toward an accurate, SS-like sound rather than a lush tubey sound. The ST-100 is smoother, with better bass precision, but based on my examination of the circuits, that most likely results from the higher-grade caps and resistors, which can be custom ordered for the CM3.
While I liked both amps, I found the CM-II had superior musicality - for whatever reason, it was simply more involving. Both lean toward an accurate, SS-like sound rather than a lush tubey sound. The ST-100 is smoother, with better bass precision, but based on my examination of the circuits, that most likely results from the higher-grade caps and resistors, which can be custom ordered for the CM3.