BigWill,
Let me guess; you bought the Sony 300-CD changer (I forget the model number) right?

I have the same one. I believe it is 21 inches deep. It barely fits on the very bottom shelf in my current entertainment center. I had to remove the back cardboard piece that keeps you from seeing the wall behind the unit in order for it to fit with the cables attached.

I will be building a flexy rack to house my components. I'll be going w/24" deep shelves.