2000 Cadillac Seville

Either way you'll need an integration adapter.  If you decide to keep the stock head unit (which I'd recommend so that you can keep using the cd changer, plus it makes it easier to keep the On-Star), all you need is the VEN4 which will adapt the bose head unit's output to one that is  compatible with your aftermarket amplifiers.  As far as using the existing speaker wiring, it is possible but you'd have to figure out all 8 wires by hand.  It'd probably be easier (and sound better) if you just ran new speaker wiring.

If you replace the head unit you'll lose your cd changer but on the other hand it will be a little easier to hook up the aftermarket amplifier(s) than if you had the stock head unit.  However you need a special adapter in order to keep the On-Star.  I'm not sure which one it is but I think PAC makes one that will work.  You might want to email them to verify this.

Thanks for your reply Ethan

Well im not sure that I want to keep the On-Star anyway. Im not even subscribed to it but you nver know win you might want it. As far as the CD changer, I can allways replace it with an Alpine. My maine concern is what else in my car goes threw the hu other than the On-Star and the warnning chimes?

 Mike

umm I'm pretty sure this year/model vehicle does not have a Class II stereo;  therefore, not even the warning chimes should depend on the factory stereo being in place.

Basically it's just the on-star and also the steering wheel audio controls if they're present (although usually the SWI-X from PAC will let you continue to use those even if u get an aftermarket stereo).