really helpful bit of info for anyone reading this thread!
The benefits of the a dedicated streamer over a Bluetooth connection is a dedicated power supply asd circuitry around the DAC chip and the output stage of the analogue output, additionally Bluetooth is a lossy method of streaming audio - it's throwing away what frequencies the codec is deciding we can't hear, also notifications on your ,mobile device will also be transmitted and audible.
A streamer will pull the stream from the service and have dedicated control. Although Spotify is also a lossy service only offering 320kbps MP3 audio streams, on high end systems the difference between MP3 and CD quality is noticeable, the differences between CD quality and HiRes audio are smaller.