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: http://archimago.blogspot.nl/2016/02/measurements-google-chromecast-audio_27.html
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.