Apple basically limiting this to Apple Music makes it kind of extra expensive. Should have at least fully supported Spotify. Apples aggresive policy when it comes to Siri on 3rd party services is kinda lame. If they can't make money of it... well no or only very limited support. I mean there was a cydia app to control spotify with Siri... So, this, again, is an arbitrary limitation by Apple. I don't see how this wins agaist Alexa/Sonos...
Anyway, since Apple limits Siri to a few chosen countries, this is only a massively overpriced Airplay speaker in the rest of the world...
Sounds a lot like the other reasons for the HP... "I'd like to buy a HomePod -how do I justify it?".
If you want to buy it, because you want to have one, just buy it and be done with it, but don't wrap some generic arguments around it. I don't see where Echos and/or Sonos couldn't have done that already long ago. Let's be honest here, to YOU both will likely sound bad compared to your HiFi system. Your wife, however, likely won't even notice the difference between the Echo solution and the HomePod.