Thanks for all the input. I didn't want to say this at the outset, to avoid prejudicing responses, but Spotify did sound good to my ears, just different. I couldn't put my finger on exactly why. The others sounded a bit richer (More ambiance? More detail? I really couldn't tell.)
Generally, I like cleaner, more analytical sound. The Sabre DAC chips sound best to me (though, except for the latest releases, they emphasize the highs a bit too much). The Eversolo A-6 Gen 2s that I am using tame the highs a bit. I'm using a Loxjie D60 as an external DAC on one of them. To me, the Loxjie is great for streaming movies and TV, but a little too thin on music for my taste. The A-6 plus the Loxjie seems to give it just the right amount of extra depth and ambiance. The A-6 alone isn't bad, but I'll probably add an external DAC to the second unit as well. (Just waiting for one that has analog inputs for my turntable).
When I did my trial of Spotify, about a year ago, it sounded more like the Amazon Music Roku app going through the Loxjie 60. But a bit thinner than Amazon Music Unlimited. I guess that's the best way to say it. The plan is to switch to Spotify when my Amazon Music comes up for renewal in a couple of months and see how it goes. I don't know if I want to get involved with Spotify Connect, though (or if Spotify will give me another trial of the regular app). Unless something goes horribly wrong with the Spotify app on the Eversolo, the idea is to use if for a few months and see how I feel about it then.
I did do trials of Tidal and Qobuz when I bought my first A-6. Tidal sounded best to me -- but it wasn't gapless. Qobuz was okay, but there was basically no tech support. No email address on its web site. No way of communicating with customer service. Therefore, I am not keen on doing business with either company. And the library size was so much smaller than Amazon or Spotify, I didn't think either was worth the aggravation.
Thanks.