pareng nels76, mukhang matinding stress test yan ha... the 333ES is rated 105w/ch at 8ohms and 140w/ch at 4ohms... i can only imagine the stress that your mighty ms-912's are undergoing at the point of clipping.
with a VU meter in the amp, i can see that 95% of the time the power output is only between 0.3W to 10W, spending most of the time at less than 2W when playing vocals... but during dynamic peaks, and especially when using the #6 drum track, i can easily reach 130w/ch and above.