What you want are IR Zones. I do not believe any power related solution will work. You might try shileding the TV's IR receiver so it needs a direct on signal by using some sort of tube in front of the receiver.

I do not know if the TV's allow their remote controls to have different device codes, I suspect not. Sony does that as do other mfg's for many classes of products. If the TV remotes allow for selection of a remote control device code or sub code you are home free.

Since I do not use an RFX9400 for IR I do not know if it has separate zones but I am sure someone here does. If so It should be doable by selecting different zones (RFX9400 IR Output ports).