Welp, that was fun for a little while. Then it wasn't.
The "put in new stuff in my system" part went fine. I will say that the XFX RX 5700 XT THICC graphics card is aptly named. Holy sheep, I didn't think I could fit the behemoth into the case for a while! It stretches the full length of a full tower interior with zero room to spare. Three 9mm ... maybe 10mm ... fans. For all that, it is amazingly quiet. That was Saturday. The only "mishap" was that I didn't realize "clone the drive" really meant "CLONE" the drive -- complete with its size! So now I have a 500 Gb SSD that thinks it is a 256 Gb drive. Oh, well, I'll figure out a fix for that later.
Then came "put the old system in the old, old system's case." That went fine up to the "now let's install Windows part." At midnight last night, after entering the (*&$&!! key so many times I about had it memorized, I gave up. I confess, there was shouting. It would get to the "Enter your Microsoft Account Password" screen and poop out -- screen went dark, and nothin' but nothin' was happening.
This morning I was trying again when I accidentally unplugged the machine. I didn't notice, and the subsequent complete lack of life made me suddenly realize -- it's the power supply! One trip to Best Buy later, it is chugging along quite merrily. I think the old PS was just barely adequate for the old motherboard/graphics card. When faced with somewhat more modern and high-powered stuff, it couldn't quite cut the mustard.
I'm frickin' exhausted -- I always forget what physical work building one of these things is.
Thanks again, everybody.
p.s.: New system is amazing. I can do stupid stuff faster with more energy!