Just thought of something do you still get the interference even if the headphone button on the dash is not pressed? You shouldn't need to push that button as I think it activates the factory IR and you have a seperate\independant transmitter. If its not pushed and you are still getting interference it is probably transmitting whatever is playing on the HU.
I put tape on the outside. Some black elctrical tape so you cant even notice it. I may put it on the inside just cause I'm anal like that. I like keeping things clean. But yeah, it helped No interference of the two receivers when I cover the factory IR. I havent tried not turning on the headset button in front to keep the Factory IR from being activated.
I don't have any idea how they would of hooked up your game ports (two of them?). You say one has RCA's, I would guess that is just plugged into your DVD for AUX and the other is a power inverter. Sorry I can't help you there.
Lets say I take out one of the power boxes. The one without the RCA jacks. Where would I be able to install the box that has the RCA's and outlet to where I would be able to get either constant power (has an on/off switch on the box), or power when the car is turned on/off. I think it may be better to have it connected to where it would turn off/on thru the ignition in case the kids forget to power off the box. The kids eventualy will forget to switch it off. So it would be safer to have it connected to the ignition