Adding DSL to existing wireless network but in different room than existing router?

I am looking at the following setup and I need info on how to do it:

Current configuration:
Top floor:
Room A:
PC with Wireless card and Gigabit on board wirelssly connected to
Router Downstairs.

Downstairs:
Room B:
CableTV->Cable Modem->Linksys 54Mbps Router

ReplayTV with 10/100 connected to Router thru RJ-45.
Xbox with 10/100 connected to Router thru RJ-45.
PC with Wireless USB and 10/100 on board connected wirelessly to
Router.
Printer with Wireless Adapter connected wirelessly to Router.

I'd like to connect a DSL modem on the top floor in Room A. How can I
connect the new connection to all the devices mentioned above so that
they can see the DSL modem connection?


Thanks