I finally stumbled upon this fancy cable thread! The only high-end cable in my collection is the Shunyata Delta v2 NR. I have it connected to my Ferrum Erco. For whatever reason, this power cable (and other Shunyatas that I've tried) only seem to benefit DACs. I tried another Shunyata (Venom v10) on my Stax amp and it did absolutely nothing. Maybe because it's a high-voltage, low-current, Class A amp whose current draw doesn't vary much during transients. But the Delta has a pretty pronounced effect on the Erco, and surprisingly also on my FiiO K9 Pro. I personally think that with the Erco, the Shunyata Venom and Delta cables make a bigger difference than the Hypsos power supply. I didn't hear any difference with the Hypsos; I did hear a difference with the Venom, and more with the Delta. When I asked for a demo of the Erco, my dealer gave me the Hypsos and the Venom too. I was skeptical of the Venom, but after trying it out on the Erco, I ended up getting the Delta as he gave me a substantial discount on it.
My impression is that the Delta intensifies dynamic swings across the entire frequency spectrum. The Venom mostly improved bass dynamics and impact, but the Delta improves treble dynamics too, though with perhaps slightly less noticeable bass impact due to the added treble dynamics. It's similar to having a dynamic expander plugin enabled across the whole frequency range. Bass notes feel more physical, like there's a punch in your head/throat when they hit. Sort of like chest punch with speakers, but localized to the upper throat and lower nasal passages. That's the most noticeable change. Vocals have more pronounced attack and decay and sound more open as a result. Treble is crisper, more dynamic, and more textured.
That change to the treble is a double-edge sword though, because it can push some headphones into being harsh or sharp sounding. My main example is my Shangri-La Jr. It has a lot of treble, and I always liked how smooth that treble is despite being so elevated in quantity. Well, the Erco intrinsically adds more dynamics even with its stock power cable, and the Delta bumps that up even further to the point where the sound got a bit piercing to me on some tracks because the dynamics compounded the level of treble. However, it does sound more detailed and "alive" than it does with the stock cable. I just let my brain get acclimated to the sound for a bit and kept the Delta on the Erco for that maximum punchiness.
I don't think I would have paid list price for the Delta; the improvement over the Venom-X (which I demoed for a few weeks) isn't that large, all things considered. But with the dealer's discount, it was only $200 more, and at that point, why not? I certainly don't regret the purchase.