oh....thats a bit harder. (for some reason i read your post as msp {speed protege})
the good news is the bose head unit has 2v low level outs already, so you dont *need* a high low converter. the bad news is its a bit harder. you would use a twisted pair type rca. cut off one end, and tap into the signal wires before the bose amp.
another option is the high low converter and get the signal from the factory subwoofer's speaker wire. make sure it has a pretty high power rating as the subwoofer speaker wire is higher then the really cheap hi/lows were designed for.