I use 2CH stereo to listen to mp3's made from CDs using the Android App. I've ripped the mp3's at cd quality levels using ffmpeg in ubuntu. When streaming from the Android App you get the Yamaha RX-A830 to do the Digital to Analog Conversion and the sound is awesome. According to the front display in 2Ch stereo mode the subwoofer is on too. Plus you can hear it. My only compaint about Android is that it keeps duplicating my music and I don't normally listen to each song on the album twice. I'm on Android 4.2.1 and my tablet and phone aren't going to be updated to the versions required to stop this issue. So every time I go to play I have to open settings, media, delete all data, reboot, and then get a single song per album. Apparently Google didn't realize that not everybody wants to store their music in the cloud and download it every time they play it.
Instead of party mode, once you are streaming to Zone A, you may select the same digital source for Zone B, and get stereo in both rooms. I don't like party mode as I don't want my center speaker and rear speakers form playing back stereo sources. If I'm not using Zone B I do occasionally use the "Cellar Club" to listen to my jazz. But most of the time the original Stereo is what I want to hear.
Yamaha RX-A830, Qysonic Array Tower Mains, Boston Acoustic Center, Custom 12" 300W Sub, Infinity Rear.