[Sephiroth]

I've done the following:

SH --> Extreme --> Powerline --> Mains --> Powerline --> Switch --> Various + A Express

The wireless network is extended through the wired connection although you can plug the A Express into a mains socket elsewhere and try to pick up the wireless from the Extreme and extend that. I can understand why you might want to do that and you'd have to configure the A Express differently.