Do you have a technical question that doesn't really fit a specific console? Want some general info on electronics, hacking, making cookies, etc? Here's the place to ask! Go nuts.
Connect the speaker out port of your PC to one of your stereo receiver's Line In ports. (Get a headphone jack Y adapter so you can still use your regular computer speakers.) The speaker port isn't strong enough to drive those speakers on its own; you need an amplifier or stereo unit.
Then you're going to have to buy an amp or a receiver. Simple as that.
Get an old one at the Salvation Army or Goodwill if you want to be cheap; they'll sound just as good. (Then again I've always liked 70s and 80s stereo equipment better than the new ones...)