Ah the endless audiogon churn between those who pursue what should sound good versus those of us who only care what actually sounds good! I seriously don’t care what happens at or above 100kHz. And for vinyl playback, any significant signal below 20Hz becomes rapidly destructive.
Modern SUTs have plenty of bandwidth for high end vinyl playback. If I felt it were lacking up top, then I’d probably like the supertweeters on my Tannoys but I actually hate them.
If extreme bandwidth is the goal, then DSD should be the focus.