I would buy a ADSL Router/Ethernet modem, i'm using one at the moment on my PC & A4000T & Laptop.
I have 1 internet connection, the ADSL router is configured with DHCP and allocates each connected computer with an IP address and DNS.
This way you can all be on the interent at the same time and all on one connection.
As for speed, i have found since moving over to an ASDL/Ethernet Router my connection is faster regardless if all machines are being used.
Obviously you can use wireless connectivity as the combined ADSL/Ethernet/Router (this is one box im talking about which cost around £80) has 4 hub ports as well.
