Power = Current X Voltage
The misconception is that speakers such as Apogee needs a lot of power, what it needs is high current type of power. AMG is designed to output a lot of current, so it has no problem driving Apogee. That means, at the same power, AMG has more current whereas ST-10 has more voltage.
Some people choose to buy amp with ridiculous power (that includes Nuprime MCX series) but keep in mind that amps that are designed for such high power > 300W give up some refinement and details. Higher power = higher noise in entire circuit and parts. That's why most Nuprime amps don't go over kill with power.
You should have the same type of amps if you are going with bi-amping (perhaps one stereo amp plus two mono amps). I think ST-10/10M or AMG will fit your need but since they sounded different, I suggest that you contact Jye at firstname.lastname@example.org with your music preference. He is our product manager and golden ear. Support is a shared email so you need to address your email to Jye.