Vlad,
any switch will support DSL sharing but you need to be sure of a few things first:
1) Does your ISP give you multiple IPs?
If so, then each comp just gets it's own IP.
2) If you have only 1 IP then you need to:
A) Share that IP through a hardware solution such as a router
or
B) share that IP through a software solution like Sygate or ICS.
As for the Linksys 5-port EZX55W, it shares port #5 with the uplink port so it can do only 4 computers if you are using the uplink port for DSL/CABLE sharing.