New to Digital

I am a novice with digital music, and would like some advice on some digital options that are not cost prohibitive.

I have a Yamaha A-S701 amp, a Yamaha 
YBA-11 Bluetooth Wireless Audio Receiver, and ADS L9e monitor speakers.

I currently just use Amazon Music from my iPhone Bluetooth. I believe that I can do better with sound quality, and am interested in your  thoughts.

Thank you for the input.
One additional question... The Yamaha A-S 701 has 24-Bit/192 K Hz courtesy of a Burr-Brown PCM 5102 DAC.

That is honesty “Greek” to me, but wondered how that built-in DAC would compare to the DAC’s you’ve mentioned 
I don’t have any experience with PCM 5102 DAC chip. The Node 2 uses the Burr-Brown PCM 5122 chip and I can say from my experience that SQ is quite exemplary given its asking price. 

Others have reported here that Node 2 does sound better with high quality external DAC like Brooklyn or Ayre Codex. 

Check out this review for better prospective on Node 2,

The Yamaha is an excellent amplifier, and that includes the inbuilt DAC. Hence I fully agree with the suggestion to get a Chromecast Audio and use its optical digital output into your Yamaha. See here for a serious review with measurement data: Without spending a real fortune, it is hard to imagine you can improve on this, unless your listening room is huge and your speakers very inefficient. I use one a seriously revealing system and I am perfectly happy. It will be much better than the bluetooth connection.
The sound quality of MQA is controversial. I think there are legitimate arguments for the view that it is in fact worse, and not better than ordinary 16/44 redbook cd quality. In the US Tidal and in Europe Qobuz will give you a streaming source for 16/44 quality, and I would not worry about it: there is enough research to support the view that lossless 16/44 is as good as you need for a perfect signal. In fact, there are good arguments that even the lossy 320 kbs Spotify stream is indistuinguisable from full red book CD. I am not sure - I thought it sounded better on informal listening, but proper comparative blind listening tests suggest few if any people can really hear a difference (I could not under such controled conditions). Anyway, I would never spend a penny on MQA.
If you ever consider spending serious money, I would suggest looking into modern speakers like the Harbeth M30.1. Your speakers are about thirty years old, and that is old - speakers do degrade with age. Also, speaker technology has improved considerably. Speakers make a real difference. But for now, enjoy the digital age.
I absolutely love the Yamaha amp, so for now, I think the Chromecast Audio makes the most sense for the money.
I’ve  been an ADS fan since the late 70’s in college, and although mine still sound great to my ear, I also realize speakers have come a long way.
Thank you again for the suggestions!
+1 willemj, I concur with everything you wrote.

In my opinion, DAC's and streaming music are in an early stage. They will evolve quickly, so investing in the 'best' now will be an effort in futility.
For me, buying a DAC that the manufacturer can provide updates is an important factor. 
That being said, companies like Ayre (Codex) and Schiit (Gungnir and Yggy) offer a great product at a very reasonable price. 
If you want to stream to different rooms, the Bluesound Node is a great cost effective choice-And, you can output to a better quality DAC, too(though the internal DAC is pretty darn good, considering the price).