I didn't see PlayFi mentioned. It came out before Denon HEOS. I believe Phorus developed it, and DTS bought it, maybe wrong on that history.
I won't regurgitate all the benefits, easier to read up on it at play-fi.com.
This is essentially an open system that leverages your existing WiFi, vs. the proprietary nature of Sonos. I love freedom...
Lossless audio capability. Connect and control with your iOS or Android device or PC.
You can buy Playfi enabled speakers to plug and play, or you can buy a playfi amp, or a playfi connector to plug into your amp/receiver and listen with your existing setup.
Definitive, Polk, Wren and Phorus make some or all of these options.
Multiple streaming audio options, as well as playing from your music library.
I have tried the little polk speaker, then upgraded to the Definitive W7, and W9. Very decent for what they are, plug and play single speaker, with the option to setup two in stereo. In the future I will add a playfi connector/pre device to connect to my main system. Whole house sounds, can pick and choose what zones/rooms to play from the app.
The app works well, but I think it's not the best designed in general. I have read some negative commentary on the app vs. Sonos. Nice thing is, you can have equipment from any of the people making playfi enabled devices, and any playfi app will control them all. I use the definitive flavored app.
What I like about playfi is the openness of it. With vendor specific stuff, like Sonos, HEOS, and now Yamaha MusicCast, you're vendor locked.