what kind of cd player did you get and what kind of I pod input does it have?
Most aftermarket CD players have an AUX input these days which is nothing more then RCA cables, so you can plug any audio device into them, even an old walkman
If your aftermarket CD player controls a CD changer then you can get an adapter that will also supply you with RCA cable inputs, again youcan plug jsut about anything into here, even an electric guitar (see new VW add's)
Now for my kenwood head units I bought an actual Kenwood I pod adapter, its kind of nice because once its plugged in the Kenwood head unit controls the I pod and displays the songs, etc on the screen, so this allows you to say have your I pod in your glove box and foget about it, you dont need to touch it or power it.
So no it does not have to be an Ipod unless it is a specific Ipod input adapter.