Question/Help Needed: Boomer who is totally inexperienced with DACs and streamers.

Boomer here also.  Using your Alexa to stream will give you a very compromised sound quality.  The Alexa receives the streaming files via MP3 protocol,  which is a very lossy compression codec. As suggested by several previous posters,  I  would recommend either the Wiim Pro Plus, or the Bluesound Node, and take the digital output into your DAC. I have a Bluesound Node and use both Amazon and Idagio for streaming services. The Node supports Amazon streaming in Ultra HD  (24/192). I'm not sure what the Wiim supports. You won't have voice control,  but the Bluesound app control from a phone or tablet is very intuitive and user friendly.  I  have a very resolving system,  but have stuck with the Node just because of the app and the streaming services that it supports.  I did modify the Node with a TeddyPardo Linear Power Supply, which really improved the SQ.  I now use streaming for about 90% of my listening. Good luck with your audio experience!!

I use the coaxial out on my Node, into a PS Audio Directstream DAC.  The optical will provide the same resolution,  but perhaps a bit more jitter (some may debate this). If the Wiim Pro Plus is what fits your budget,  I think you will probably be very happy with it.  It will be significantly better than streaming from an Alexa device!