Okay folks, got a Schiit Modius yesterday and did some "A/B" testing with a couple friends using a laptop as the music server.
Hooked up the DAC with an optical cable from a 2nd Airport Express, and then RCA cables to the amp. That way we could go back and forth between the Schiit DAC and an Airport Express over wifi feeding the AMP.
After about an hour of listening & comparison no one could make out a discernible difference.
Next, thought maybe going through the Airport Express is a limiting factor. So hooked up the Schiit DAC directly to the laptop via USB and then did the comparison with an Airport Express over wifi. And once again no one could tell a difference.
So there are only two conclusions that can be made. The signal from the laptop is so bad the Schiit DAC can't do anything with it. Or the Airport Express DAC is pretty good as Ken Rockwall's testing indicated.
So, being part of the CLAC (cant leave it alone club) I'm going to get a streamer to go directly to Qobuz/Tidal, etc. and see if that is the key.