If you have BOSE any upgrade is a downgrade. If you have base get an OEM 12 Disk CD Changer.
If by any chance you do have BOSE but only tape (never hear of such after '98) then buy a '98-'00 OEM In dash CD BOSE HU (best update ever).
If you have base you can upgrade to BOSE (I did-it but is NOT going to be easy), but comparable in price (if DIY) with an aftermarket system, but WAY better sound quality and less issue after with the car.
But I already told you so on the other thread...
In the end is your car so all I am saying are things to consider, in the end is YOUR decision. Listen to as many opinions as possible, but keep in mind I am not trying to sell anything, some other opinions will come from people trying to sell you an aftermarket system. Have that in mind…you are not a fellow Cadillac owner, just a walking wallet.