So there are a few things about all this that I find confusing:
1. If your modem/router is coloring your sound in any way whatsoever, it's broken. You would feel this not just across your audio devices but all your devices in terms of increased latency, connecting stability, etc. This is not a debatable issue - if routers don't meet a variety of standardized criteria, they flat out won't work with the rest of your network able devices. How would they?
2. Power availability also doesn't seem to be a debatable issue. You have enough or you don't. There is some wiggle room around things like THD, IMD, filter speed, etc. depending on your age, listening habits, environment. I don't personally feel these things are audible but there's a small argument to be made. But power is not one of them - it's literally a binary choice.
Given we both have Stealth, I would encourage you to play back Max Richter's Cradle to the Grave on your lowest powered device, followed by next highest, and then higher and so on. For me that's the E1DA gen3, then iFi Diablo, then A90. The E1DA soft clips very early on - bass basically stops getting louder. If iFi hard clips because it's a garbage design, and the A90 plays clean shaking my whole face with no added EQ at all. If this isn't a power availability issue, what is it? How would a transport cause this effect?
Finally, what defines "good power" and "tonal density"? If we can't agree on some objective metric, there's no hope of unwrapping the situation accurately