So it looks as though our lesson for today (and every day
) is that Peter knows what he is talking about.
There could be an entry in the XX log, but I wasn't able to identify anything that called out what was happening when XXHE wasn't able to shut down the remaining services.
Somehow Win Defender and Firewall had managed to get themselves turned on again, so I turned them off, but that wasn't the problem.
No, of course it was the AV. Though it complained that I was "unprotected," only one of about seven running AV processes was actually turned off at the time. And they make it a PITA to turn everything off, since 6 of the 7 are only off until the next reboot, while the 7th *requires* a reboot to shut it down.
So I set the one process to stop as of the next reboot, rebooted with OS minimized, then turned off the other 6 processes at a sub-level of the AV UI. Whereupon XXHE was able to stop all the remaining services within a couple of seconds and begin play. And yes, Peter, it sounded even that much better - I was glad I persevered.
So it may require some fiddling each time with the AV UI (and more to turn it back on again for when my wife and stepson use the desktop), but sonically it is worthwhile.
Now for some work in the yard, and later the multimeter to see whether hooking up a more powerful amp might allow use of PA.