So I got to looking at some old articles, and I ran across Undervolt AMD's Radeon R9 Fury With MSI Afterburner - Tom's Hardware and since MSI Afterburner finally supports doing it to the Fury Nano, I decided to give it a go and see what kind of results I could get. As you can see from the image at the left, stock GPU voltage is 1.23v, resulting in a steady system power draw (with spikes higher and lower) of 478w. On the right is a tweaked setting of -36mV, resulting in a voltage of 1.2v and a steady system power draw of 445w, net 33w lower. I wasn't able to jump down to -40 as it'd result in instability. In the article they were able to drop down to -96mV on their Fury sample, but as always different GPUs work differently. Something else pointed out in the article was how a lower voltage resulted in a more even power signature without as many spikes. Try it with your cards, see how low you can go. It'd be interesting if someone did it with an RX 480, see how much margin of error AMD threw into them.
And no my Chassis #3 fan is not spinning at the speed of light, that's the header my H105 is plugged into.