I completely agree with your thoughts on not drilling any holes. I have heard a few horror stories in relation to cutting holes in firewalls. Including the fact that your little treasure may be appraised foroverall conditionsome day. Just a humble opinion, but run subwoofer and amp systems as a temporaryenhancement to your 944. Youcan still tuck system wiring from battinto fender well then down, then underplastic kick plate (lower door frame), then tucked into theside of rear seat, up to the rear deck area. It won't be completely invisible, butif you are inclined (as I am)in keeping your Porsche as pristine as possible... remember, she'sheadingtowardher 25th birthday!