We bought an Echo Spot, and it is remarkably good for it's size. Having a display comes in very handy too. We have a Show in out kitchen and a couple of Dots in other rooms. We use the shows for checking up on elderly relatives and garage to house calls
The dots are there for the home automation stuff.
The choice is one between Google and Amazon. The former being better for general enquiries, the later better for home automation. Also a small point but saying "Alexa" seems a lot nicer then "OK Google".
I would recommend a Sonos One, which is powered by Alexa were it not for the fact that some of the Alexa functionality is compromised.
Since the Echo dots can be had for around £30 they are a good device to start with. you can pair them with a Bluetooth speaker too.
Much depends on how you like your music. If you want it loud and rich you will need the bigger speakers like the Echo or the Google Home(not the Mini).