Server 2003 5 NICs DHCP Server

I have a Server 2003 Enterprise computer for my home network, with a built in ethernet port, and 4 pci ethernet cards. . I also have 2 cable modems providing 2 internet connections. I am wanting to use 2 of the ethernet connections for the internet IN in a round robin interface, and have the server act as a dhcp server and directly connect my computer, my roomates computer, and a wireless Linksys with DHCP disabled into the other 3 ethernet cards, and have the connection going IN the first 2 nics and OUT the other 3. There are guides on how to setup dhcp servers, but my question is how do I get the 3 pci nics to push the internet through them out instead of sitting there and saying limited or no connectivity? I have tried bridging them (which then does not give an option for ICS, and apparently unbridged, I can only have one out of the 3 "senders" enabled with ICS. I bought 4 pci crds oppossed to buying a switch, bacause I naturally figured a dhcp server could control computers connected to multiple ethernet cards in the server itself. What am I doing wrong here?