Theres not much you can do to a caddy without spending alot of money so its pretty stock so far. Only major addition I have done to it has been a sound system and a tune up.
First of I started with a sony head unit. I got it beucase it was the only one I could find that was simple and had a dial to adjust the volume. I hate push button adjusting. Secondly I got some infinity 6x9 for the back. Super simple install and provided a good sound. Then I got some Infinity 4x6 for the dash. Made the base and treble sound great. Then I bought 2 12 inch Infinity subs. I had these sitting around for about a month before I got my amp. Durring that time I got some speakers from work. Three 3 inch Harmon Kardon which I put 2 right abouve the front seat seat belts and I put the other below the ashtray by the heater duct. So far with the volume up all the way you couldnt hear yourself talk. So finally I got my amp and my free sub box that I got. The first time I head the subs hit I was amazed. So after about another month of having a lame sub box I made my own. I still have to get some pics of it but its not bad for an hour or so time.
Some more pics will be comming once it stops raining and I clean the car up.