You can not be certain of the source of the music available streaming. That is why I only listen to physical media.
But you're certain of the source of the physical media? Okay.
On topic - If you'd like an improvement over the sound quality of the Node 2 then an external DAC can help, but my experience was that replacing it with a better quality streamer/DAC (the TEAC NT-505 in my case) resulted in better sound quality than adding a DAC. As a point of reference, I tried an Auralic Vega (which cost more than the TEAC), a Mytek Liberty, and the excellent DAC in my Sony TA-ZH1ES headphone amp.