Read about relays at http://www.the12volt.com
Basically, when the remote amplifier turn on from your m2-atx receives power, it activates the relay which will send 12 volts from your battery to the two amplifier remote-ons.
I have to do this really soon, and thats what i figure is the best way. I'm not sure if just splitting straight off of the m2-atx remote amp-jumper will be able to supply enough power for both amps to turn on. Anybody have information on this?