I have a Pioneer SC-09TX receiver that also toggles on/off with an IR remote. Using discrete codes alone would often result in the receiver loosing its on/off state when switching across different media devices.

My solution was to use an RFX9600 and a power sense input to read the Pioneer's power state before sending a code. This did require a few lines of scripting (which I don't like writing) but resulted in trouble free operation.