These cars are such a pain in the ass when they come with bose...it took me 3 months to figure out how to put my new head unit and subs in...i put it in first and no sound from the speakers and after doing some researching and asking around i found out that there is 2 wire harnesses that come into the stock head unit one for speakers etc and the other for the steering wheel controls...well the steering wheel control harness has a pink wire on it and that is the remote turn on wire for the bose amp to get the speakers to turn on..i went to walmart and bought this...

Buy.com - Scosche SLC4 Speaker to RCA Four Channel Line output converter

this adapter also will work for what you wanna do since you can use it 3 different ways....plus it lets you adjust the speaker levels the way you want them.......