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.

the first thing i'd do is upgrade to spotify premium ($10/mo.) or tidal ($20/mo.), which have much better libraries and sq than amazon music. next, instead of your bluetooth receiver  i would get a google chromecast ($35), which uses wifi, and connect it to the optical input on your amp (an optical to mini-optical cable cost around $7 or so)--the foregoing will be a cheap, substantial upgrade
Thank you for your advice.

Actually Amazon Prime and Spotify Premium has the same streaming resolution at 320kbps.  

Tidal will give you the best available streaming quality at 16bit/44.1khz. And MQA resolution upto 32bit/192khz but you need MQA compatible DAC to hear the full resolution.  
Any recommendations on a MQA compatible DAC?
I have a Mytek Brooklyn DAC for MQA, it's a very good unit for non-MQA as well.  They have recently replaced that with a Brooklyn DAC+, which has a few small improvements, including an upgrade to a little better ESS DAC chipset.  I think the DAC+ goes for $2150 (new).  You can probably snag a gently used original Brooklyn for much less, if your budget won't accomodate a DAC+.  I see one on the U.S. Audio Mart for $1275 today.
This unit has a wonderful headphone amp, built in phono stage and is a joy to listen to.
+1, Mytek Brooklyn DAC. At $1275, it’s a steal. 

Another inexpensive alternative is Blusound Node 2 for $550. The Node 2 will stream from Tidal, Deezer, Spotify and has an very nice internal fully compatible MQA DAC. 
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).

+1 willemj! It is always good to make up your mind without actually hearing something yourself.

If you have really old speakers you should probably start with replacing them. Some people puts most of their stereo budget in speakers and if you follow this you could look for speakers from $400 up to around $1000.
If you want to upgrade you digital part I have two ideas. You could get the Audioquest Beetle and a Chromecast. That's about $250 and should improve the sound. Or you could sell your amp and get a PS Audio Sprout, it has everything except speakers. If you like to tinker you could build a Raspberry Pi with a soundcard or spdif outputs and connect to your amp.
There is really no point in worrying about the quality of the Yamaha. See here for a test of the earlier AS700, identical but for the lack of digital inputs:
The results are seriously better than for many audiophile amplifiers costing perhaps ten times more. Its only limitation is the power output at around 2x100 watt rms. If you are using inefficient speakers in a larger room you may want more power. If not, you will be perfectly fine. Since the digital output of the Chromecast Audio has been shown to be bitperfect, there is no issue there either. I have not found any test yet of the Yamaha's internal DAC, but I would not expect anything other than excellent results.
So the only way in which you may be able to improve the sound of your system, is by getting really good modern speakers like the Harbeth M30.1. The rest of your system would be an excellent match even for such expensive speakers. But speaker choice does depend on personal preference, room size and music selection.
I had a Yamaha receiver in the late 70’s and it never disappointed.
I did quite a bit of research on this Yamaha amp before I bought it, so I am very happy with it.
Based on your suggestion and some additional research, I just ordered the Chromecast Audio with the optical cables.
Just left to decide if Tidal is the way to go.
As far as speakers, it’s unfortunate that there are no high-end Audio stores within distance to listen to the Harbeths.
I was actually intrigued with Clayton Shaw’s Spatial Audio speakers, especially at their price point.
Again, thank you for the great information.
Enjoy. The digital output of the Chromecast Audio will certainly be a sonic improvement over the Bluetooth connection.
As for speakers, I am afraid they are expensive, but they also have the biggest impact of the system’s sound. But since you already have speakers, you can take your time to save and listen. Unless your room is very large, the Yamaha would be good to drive the Harbeth M30.1. They would be my personal favourite for a very neutral and accurate speaker in a still modest size. If your room is very small, move one size down to their P3ESR, if the room is rather larger, you may consider their SHL5+.
Harbeth's Alan Shaw is firmly convinced that expensive cables are a waste of money and designs and demonstrates his speakers with basic cable. Quad's genius designer Peter Walker similarly thought they were nonsense. Well designed speakers and amplifiers do not need anything more than bog standard.
Looking forward to the arrival of the Chromecast Audio.
I’ve read a lot of posts regarding cable.
It’s telling when someone who designs speakers demonstrates that you don’t have to spend a lot of money on cables as long as your system is matched.
I will enjoy my ADS for now and start saving my money for my next set of speakers.
Thx again for all of the advice