When both the computer and monitor are on, and you turn off and turn on the monitor using the power button, or with the remote's off on, do you still get a blue screen?
If you do not, you can use a relay on the power line to the monitor controled by the M2ATX power supply's Anti-thump feature. This is used to delay the stereo amp from coming on before the sound card outputs a signal, you would be using it to delay the monitor coming on before the video card outputs a video signal.
I haven't used the anti-thump in my M2ATX, so I cannot tell you what happens when you power off your computer, if the accessory line automatically drops the P6 line and the monitor would go off before the delay shut down for the computer, or if it would remain on, showing a blue screen.
I don't know if the signal from the P6 connector is positive or negative, maybe other's would know.