Yes, you can build a good stereo system, connect some kind of streaming system and end up with something roughly the equivalent of Sonos.
But this is the whole Dropbox vs Git+Remote Backup+Your own server thing.
The ease of use and "it just works" simplicity is the feature, and every other setup compromises this to some extent.
I have a Onkyo & Dali hi-fi setup. It's a great system. And I've made attempts to make it as easy to use as Sonos.
Let's go through the things I've tried and the compromises they have:
- Harmony remote + CEC to control the TV and stereo. This is ok (the Harmony products are good) but has *exactly the same issues as Sonos: a propriety system that is subject to upgrades. I've had to throw away one system already.
- Bluetooth streaming. Tried Airplay, but there is no reliable Android support. Bluetooth is ok, but if the range is annoying if someone is walking around the house.
- Zones. My amp sort of has a concept of this, but I haven't even attempted to get it to work. The wiring of speakers is enough to put me off it.
Sonos solves all these problems. But obsoleting their speakers is horrible, and 4 years seems too short a time for this.
I'm not sure what the solution is, but some kind of maintenance fee is something I'd consider - especially for older hardware. It'd have to be substantially less than what I pay for Spotify though. Maybe after 5 years I'd pay $10/year?