How to Route internet traffic on a second T1 and leave the voice traffic as is.

I recently ordered a new T1 Internet Access from AT&T. I ordered it as a backup to my current Internet conncection, which is a fractional T. I would like to leave the current settings on the PiX/Router alone (Currently running voice and data on this fractional T.  I want to route all my Internet browsing and Email over to the New T and leave everything else going out on the existing T.
Can I set this up using the internet settings in Control Panel? \Control Panel\InternetOptions\Connections\Lan Settings\Use proxy Server.   List the internal IP address of the machine that I set the new t1 up on.
Is this feasable. Is there a way to do this change centrally, without having to go to each workstion. My workstations all use Windows XP Pro, I have two domain controllers (primary and 1 alternate)and recently migrated from Novell Netware to Windows Network.
BTW, my PIX will not allow a second T1 connection.