I wouldn't use standard computer speakers, as I doubt you'd get enough volume.
If you can stream it to your computer, you can run a 'Y Cable' from the earphone jack to the 'AUX Input' of your stereo.

If the speakers are connected to your stereo in the house, you could get a little FM transmitter. This plugs into the earphone jack of your computer, and has an antenna that then transmits the signal to your stereo receiver on a non-broadcasting station frequency. You just tune your receiver to that frequency, and voila! You can broadcast your own little Pandora radio station. One caveat...the signal does not transmit over very long distances, so your PC would have to be fairly close to your stereo...like an adjoining room. I use my laptop and WiFi for this because of its portability.

Here is a link that might be useful: FM transmitter

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Get ANY home stereo receiver. Every single real receiver in the world has a whole bunch of RCA jacks on the back for audio inputs, and sometimes video also.

And your computer. It's got a 1/8" stereo jack labeled "SPEAKERS" or "LINE OUT".

So you go to Radio Shack and you buy a cable that's got a 1/8" stereo plug on one end and two RCA plugs on the other. You attach one end to your computer, and the other end to your stereo, select the appropriate input on your stereo, and start your music streaming on the computer.

Voila, internet radio on your regular speakers.

You can play your computer audio through just about anything. Our neighbors hate us:
{{gwi:1514025}}