When you say "Stereo Speakers" do you mean the type from a home stereo system?
If this is what you mean, you will need to get a lead that enables you to plug the soundcard into the Aux port of your stereo (I've got a lead w/ 3.5mm Stereo Jack- 2x Phono (RCA) connectors) This cable runs from the rear of my soundcard to the AUX inputs on the rear of my amp.
The amplification supplied by the sound card will probly not be enough to power a proper set of stereo speakers, so it means you will need to have your amp on and it switched to AUX (or wherever you've got it plugged into- Anywhere but the Phono Stage, as this is highly sensitive and you can damage your amp) to get sound from your computer pumped through your stereo.