AirPort network with Extreme AND Express

I have an AirPort Express which functions as the base station for my network. It has the Ethernet connection for my broadband access, and is connected to my stereo iot work with airtunes.
I have AirPort Extreme in my iMac and WIFI in my PC. I also have an additional AirPort Extreme unit that I wish to set up elsewhere. My idea is that this could be the hub for printers, scanners and external HDD.
My problem is that there is no broadband access in the basement where these items are located, and I haven´t figured out a way to implement my genious idea of using the additonal Extreme unit in my network.
Do any of you have ideas of how to realise my vision??

We don't have basements here. One way would be to run an ethernet cable through the wall to the basement. It depends on how your home is built and whether there is space between the walls and if that space is common to the basement area. The use of an ethernet cable from the main broadband output would give you another access point for wireless from the basement without trying to use relays - which probably will not work very well anyway.

Regards.

Is it even possible to configure both the Extreme and Express to be part of the same network? If so, could I use the Extreme as a WIFI hub for the scanner/ printer and HDD without linking this to the Internet?