its funny, i got tripped up on that illum vs dimmer thing for the last 4 or 5 installs ive done...but it ends up being correct every single time

 

this post was useful. i'm going to use the orange-orange setup too.

 

Although I've never tried this in an s2000....

ILL (illumination) will dim your headunit when you turn on the headlights (at night).

DIM (dimmer) is connected to the +/- on the dash....when you dim the dash, the radio will dim as well.