Having a spare D-link homeplug 500, and seeing that it was rated above the router's 100Mbps, I connected 2 of them to the same router to see what happened.
It didn't work, the network stopped working only to recover when I unplugged the extra one.
I proved conclusively that this didn't work with my kit, but why not?
Is it something in the homeplug spec, or might it work with different kit?