You need to get a line output converter, which you will find on EBay amoungst other places. This will take your speaker outputs and down power them to an RCA style output. Make sure you get one that filters out noise (so don't just buy the cheapest one) otherwise you will hear electrical interfearance on the output. A company called Stinger make several models. Of course to get the best clarity your better off buying a stereo that has pre outs on the back already, hope this helps.
Chris Skillen
April 2008