@toddcowles while I'm not saying this is your specific issue, I have a local contact who's complaining about the exact same issue you are now and he also runs those same AA cables you have now, fwtw. Coincidence, i don't know. They did not have the problem until they ran those cables you have now. Will be interesting when you report back about the upcoming changes you'll try next. If you plan to keep the HS speakers, I believe you can make adjustments elsewhere, maybe.
Also, not to derail you too much, but what preamplifier are you running wiht the X150.8 amp?
I heard that amp at a show a few years back at a show with some efficient Zu Audio speakers, and holy cow it just sounded terrible (overly fatiguing) with the volume turned up. All I could think of at that moment if they were to continue to run those speakers, was for them swapping out the preamp and swapping out the cables for something a little more forgiving, perhaps. Will be interested in your update after you swap some of that out and try others. Best of Luck.