That's the path all streaming devices are going down now. Chromecast is literally a SoC - to stream web content you just pass across a URL and it handles the rest. You can get a range of speakers with it built in.
Quite a lot of sub-$100 speakers have Google Assistant built in and can operate entirely on a standalone basis pulling music in from Spotify with no other device involved.
Alternatively you could buy something like the Yamaha MusicCast WXAD-10. It’s a little Spotify Connect enabled box that you plug your speakers into and it has a price tag of about 140 EUR in Europe ($160).
I haven’t tested it or listened to it myself but the first and only review I checked was favorable.
That’s not to say that one should buy an AV receiver for this purpose alone. I only mentioned it because (a) some people might have a Spotify Connect capable receiver already without being aware of it or (b) they are planning on buying a receiver anyway and so might wish to consider this alongside their other criteria.
It does... also got a google home mini that I use with it (was bundled in with something else I was buying). The voice recognition seems to be a bit better with Alexa though.
I was unaware that you could now get speakers with that kind of horsepower built-in. What's their typical use-case?