DON'T start cutting anything up! That's just crazy. I know you found a solution, but here it is, just in case someone else needs help....
HI FI SYSTEM #1 (Main) - Look for the OUTPUT connections on the back of the unit (some don't have this). Plug in your RCA cables, or whatever type of cables fit the OUPUT connections (almost always RCA, unless you have some professional unit)
HI FI SYSTEM #2 (Aux) - Look for the LINE INPUT or AUX INPUT connections on the back (or front) of your unit (the red & white colored connections). Plug the RCA cables you have running from HI FI SYSTEM #1 OUTPUT into the LINE INPUT. That is pretty much it.
Remember, not all systems have OUTPUT connectors. If yours doesn't, your out of luck, and you might have to resort to using your HEADPHONE jack and modifying your cables or buying a special adapter. That's a whole other topic!
Mark, May 2006