Windows Server 2003 as gateway

I have a ADSL router connecting to Internet.
Then a switch connected to the ADSL router.
And lastly a server and a few PCs connecting to the switch.

All this while, the router will be the gateway for all the PCs to go to
Internet.
Would it be possible for me to configure the server as gateway for all
the PCs?
Whenever the users want to go to Internet, then they have to go through
the server and from the server go through the ADSL router and to the
Internet.

The reason behind is I would like to setup a network monitoring tools
at the server to monitor which PCs is using the most bandwidth to
Internet.

Or, is there any better suggestion?



Peter CCH