You are correct ceh4702 in stating the quality depends on the sound card, but if dydt is just trying to pipe live radio broadcast from the internet to her stereo almost any sound will be adequate.
dydt first in order to do this check your sound card hopefully it has a line out connector. This may be 2 RCA plugs, but is most probably an 1/8" stereo mini phone jack. If it doesn't you can use the speaker output, but turn down the audio output volume in Windows or whatever OS you are using (distortion is bad). You will want to find either a cable with an 1/8" stereo mini phone plug on one end and 2 RCA plugs on the other or an adapter to do this and an RCA cable. Also make sure your stereo has a free set of RCA inputs. Be careful if using an input marked Phono as some stereo systems have a built in RIAA preamp on this channel due to the very low output of older phonographs. That's about it.