Just had the CDC40 out, to fit a Dension.

On the wiring block there is 2 cables sockets labelled, SW+ & SW- I'm assuming that these mean Subwoofer + & - (no wiring though)

was a subwoofer an option?

Also I noticed that the wiring labelled RSA Power and RSA GND are present so makes me think that these are the wiring for Rear Seat Audio....