Something to do with my setup perhaps, 3 channel only, analog speakers?

Perhaps without surrounds the effect of the center width parameter is more obvious.

Drobo-->FW 800-->mac mini-->Ethernet
Transporter--> Wireworld Eclipse 6 coax-->Meridian G61
G61--> Nordost Red Dawn-->Primare 30.3
Primare-->Ocos--Vienna Acoustics Beethoven/Maestro