Updated this information with attempts to put Rpi0 with USB audio into tic tac container.
https://other2funstuff.blogspot.com/201 ... nsive.html
Hope this helps.
Also compare and contrast USB Audio to Chromecast Audio because the Chromecast has great functionality with lots of audio software. Other very low-cost solutions exist that don't have an amplifier including the items in the photo below (counterclockwise from the top: Rpi0, USB audio card, USB audio card with optical SPDIF, Chromecast Audio with analog and optical SPDIF).
The Chromecast Audio puck is $25 US and has the functionality of a wifi enabled Rpi with audio output, similar to the Rpi0 and USB SPDIF output card shown above. There may be audio quality differences. Through software, I am thinking that the USB audio can be configured to mimic the Chromecast Audio functionality. This may require some skilled software people. It is quite easy to connect many audio services to the Chromecast Audio puck, which I would think if the USB audio can mimics the cast functionality would be very beneficial for marketing purposes.