The next day, a Saturday, I reconnected the amps using balanced XLRs. Luckily, the 990 has two balanced sub outs.
I put on the heretofore annoying disk, Vital Idol, and was struck by how much better it sounded. In fact, it sounded fantastic. I switched back and forth between analog audio bypass (Oppo BDP-83SE analog out to the CD inputs) and digital in (Oppo via optical cable out to DVD inputs) and really couldn't discern any difference. They both sounded great, and I listened to the whole darned CD without flinching my ears once.
Then I tried classical, dance, acoustic guitar, the ever faithful Heart "The Road Home" live set, jazz, Buble, Groban, Sade, Keys, Lady Antebellum, Beatles, ... couldn't find a thing that didn't sound wonderful.
Did the amps change? Did I change? Did the balanced cables make the difference? Don't know; don't care. Don't plan to spend time worrying about it. The amps are effortless, boundless, silent workers creating high quality amplification with no fuss or bother. This camper is happy!
So there it is: Made in CA amps with a seven year warranty attached to Made in CA speakers with a five year warranty. If I could find a Made in CA pre and a Made in CA source that I both liked and could afford, well wouldn't that be something?