"One wonders where the chaps and chapesses put their Samsonites and duty-frees given the number of consoles in the current E-3A/C"
They go into the luggage storage area behind the radar technicians console. (Same place as the E-3D). The E-3D has an empty space where the extra E-3C consoles go. It is referred to as the "ballroom" and makes an excellent area for crew briefings and the resident card school on transits. I believe that the hard points are available under the floor for the consoles to fit into the E-3D. However, it would take big changes in the aircraft software etc to fit them.