Streaming Spotify

Too answer your question in a very general sense - 

Phone DAC - if you can, definitely move to a high end DAC over the one in your phone.    Keep in mind it mpeg music is what the phone designers figured would be the most common format.

Bypass Preamp - if you don't need the controls and the external DAC has a volume control option, then you can easily bypass it.

Preamp DAC - some do, some don't.   Check your owners manual to be sure.

Hmm. Today streaming can sound better than red book CDs and certainly FM tuners. The advantage is a nearly infinite music library and  low cost ($14.99 / month). The best streaming service for high quality sound right now is Qobuz, and secondarily Tidal. To do this a high quality streamer (think Aurender) and DAC is required. This can be a single box with both DAC and Streamer (think Aurender) or a separate Streamer and DAC . One can use a PC or iPad as a streamer, but that is not as high quality as a separate (no, a PC are not as good).
 

So streaming can be as good as other digital sources or even analog, but it requires carefully choosing and investing in a streamer and a DAC, and with carefull research, you get what you pay for. So if your preamp cost $2k and your amp cost $2K you should think of investing $2K in a streamer and $2K in a DAC and your jaw will drop, you will have access to basically all music and you will be amazed. 

Thanks for your response. Here’s something else concerning streaming with a DAC: the connection to the amp. Since the amp inputs are connected to the pre-amp, would I have to choose which music input -- preamp or dac.

OR is there another solution that gives me the flexibility?