Thanks for the suggestions, Chrisc31759.
1. These trigger-controlled power outlets would fit the bill, if they weren't so expensive. The Xantech AC-1 is nearly $70 on Amazon, the Niles is even higher, over $100. I was hoping for a less-costly solution, but I'll keep these in mind.
2. The smart power strips, from what I understand, cut power completely when they "sense" that the components are in a stand-by mode. I guess this would work, but the receiver would need to be plugged into the same power strip to provide the "stand-by" status. Not sure how well these actually work in practice.
3. The thermostat-controlled unit from Coolerguys is exactly what I have now. I'm trying to use it without having to leave it on all the time, switched to turn on when the receiver is on. The power converter you linked to is a replacement for the one that I bought with the fan controller, and the Noctua fan is nice - but I've already for four nice 120mm Scythes mounted on the rear panel.
Out of the three, I think the trigger-controlled power outlets come closest to what I need. But, I'm still wondering if there's a simpler (and cheaper) relay that can take the 12v trigger from the receiver and switch the fan controller on/off, while the controller is plugged into a normal outlet.