So after a full 5 weeks of constant usage, I can say the Zu Union 6 Supreme is happily staying put in my house. They've broken in very nicely, and from what I read, they will settle in even more over next month or so. The strident is gone, the top end is open and airy, the low end is satisfying enough (although since I already have dual REL T5i's in stereo I leave them hooked up with just slightly adding to the very bottom.
As mentioned before, I had a lot of changes going on during the process, which made it hard to dial it in from a constant setup perspective. I think the best change was adding a Sonnet Morpheus DAC and Denafrips Hermes DDC. My chain looks like this:
Innuos Zen MK3 -> Denafrips Hermes (USB) -> i2S to Morpheus -> RCA out to amp(s) (Valvet E3, and Oliver Sayes 421a tube amp)
I added two new PC's from Audio Art during the process.
My biggest insight is the Zu's are the most revealing speaker I've owned. Every change I made you could hear it, whether a cable, the DDC, etc.. good or bad, the Zu's let you know... So dialing in has been the key as well.
Compared to my previous statements, I no longer feel the Zu's are strident or closed in. They throw a huge soundstage, and this is the first time I've experienced front to back placement more extremely. Ex on Eagles live Hotel California track, you can easily tell when the drummer kicks in he's behind the other performers. so you get a 3D soundstage on top of the left to right.
When compared to my Omegas. The Omegas still have a super sweet midrange, at the expense of being more forgiving. To me that means losing a little size of the music, and a little detail. They are actually more similar than different, but with the right gear the Zu's are on top. I'm actually thinking I'll sell my Omega's (Vintage 8 Dual High Output) and buy a used pair of CAMs (Compact Alnico Monitors) to have as a secondary pair.
@whoopycat put some major hours on yours, and the roughness is all but gone on mine now.