What do I need to Stream online music?

simple answer:PC>USB cable>DAC>amp>speakers or headphones>Pandora/Tidal or similar music service.There’s a good PC Audio Forum here.Head-Fi.com is also really great for reviews on just about every piece of gear out there for streaming audio.There are also many choices out there now with amps that have the DACS built in like Peachtree Audio.If you look at my headphone rig you will see how it all comes together.Good luck & welcome to streaming audio.

Thank you.  Does sound quality is the same as CD with hi end equipment?      

It is to my ears & I listen a lot.Some people who have golden ears & multi thousand $ systems might say differently.

Sonos Connect has great user interface, and very easy to use and set up. If you use Tidal you might want to add a low cost DAC like Parasound ZDac or Peachtree Dac-Itx. For Spotify or Pandora no additional DAC needed. After that there are many ways to go, but this is a low cost, easy to use, way to start. And if you don't like it, resale on these components will get you all your money back !