When using the Actiontec powerline adapters, you created a pseudo Ethernet connection between the AirPort Extreme and the upstairs AirPort Express. As such the Express should be configured as a roaming network with the Extreme. In that case, you do not want to use the "Extend a wireless network" option for this Express, but use the "Create a wireless network" option instead.
In a roaming network every wireless router, interconnected by Ethernet, must use the same network name, wireless security type & password ... so yes, it can have the same wireless name. Your other Express, in turn, will be wirelessly extending this roaming network.
Can I have the upstairs wireless named the same as the one in the basement? and will everythign still be on the same network?
Apple's setup "wizard" in AirPort Utility will automatically configure the remote AirPort correct in a roaming network configuration. All that you really need to do is name the remote AirPort......the "wizard" will take care of everything else for you.
Post back if you are not familiar with using the configuration "wizard" and need a few more tips.
Can I have the upstairs wireless named the same as the one in the basement? and will everythign still be on the same network?
Trying to extend a network with Actiontec ECB6000K02