OK I set up the priority in Task Manger to Real Time and it's much better now.
...If you do try that Ethernet connector, please post yea/nay if you have a chance? I too am using Chromecast Audio, and mine is hooked up to Ethernet. (Even Qobuz, which gave me fits over WiFi, now has zero interruptions over the wired connection.)
The only other thought I didn't see in your thread with @BillG is the 5ghz WiFi band, which of course does not have to compete with the kitchen microwave... though I'm sorry to say I don't remember whether the Powergate has that band...
Lastly, I should prolly add that I have gigabit Ethernet to the house, which is prolly cheating a little, and still I had to pay attention to how many hops between my first and last boxes to get those big audio files to stream without breaks, without Roon, and without a dedicated machine to act as music server. (Roon was a helpful diagnostic tool in that effort because apparently it can "see" the speed of each hop.) I'm happy with the Powergate as a great bargain, but unfortunately I've just read the Benchmark review and I now have a new toy for my OCD twitch list!