The Chromecast Audio that you have can be used to address a NAS using Bubble UPnP free software. I have not done this myself, but many have. Not sure how this would work with a laptop, but I am sure there must be ways. There is nothing wrong with the sound quality of the CCA, and certainly not if the budget is tight and you are using 16/44 source material.. I think it is the biggest audio bargain in the the market. If you ever have a bigger budget again, all you will have to do is add a good DAC with optical input, and you are all set for high end streaming with the service of your choice. Its current maximum is 24/96, which I think is more than good enough for audio perfection: http://archimago.blogspot.nl/2016/02/measurements-google-chromecast-audio_27.html
Alternatively, and short of just using a cable from the probably crappy analogue output of your laptop, you could use a Behringer UCA 202 usb DAC. It is not the world's best DAC, but it is cheap - very cheap, and great value fo rmoney: http://nwavguy.blogspot.nl/2011/02/behringer-uca202-review.html
Alternatively, and short of just using a cable from the probably crappy analogue output of your laptop, you could use a Behringer UCA 202 usb DAC. It is not the world's best DAC, but it is cheap - very cheap, and great value fo rmoney: http://nwavguy.blogspot.nl/2011/02/behringer-uca202-review.html