[Cube] 22" & 23" cinema display differences?

[Riba]

Ok, apart from the horrible fact that 23" cinema display has a  
polished mirror apple logo instead of graphite one :), I just noticed  
that my cube speakers do not get the necessary power to work properly  
if plugged in the 23" cinema USB ports. With 22" model they worked  
the same as when plugged directly in the cube. Is this a feature? I  
wouldn't be surprised if Apple changed the specs of 23" display and  
lowered the power supplied by the usb ports...