Yeah the illumination is just from the ceiling lights. Dont forget the RX8 is 4 door, and so has another ceiling light for rear passengers. So more illumination.
I'm thinking of fitting a Brava's rear courtesy light in the rear for the rear passengers and to also come on when the front doors are open.
In regards to Caterado, 10W ones maybe too bright. However thats your choice. The ones in the pic are 5W.
Joske