Planning ISA Server – Hardware Issue

hi
i am looking for a solution to place ISA 2004 in my office. The requirement is to connect 6 Internet Connections to one ISA Machine but i cannot attach more than 3 NICs to my system as i only have 3 PCI slots available on my system. Can anyone please suggest a solution that would help me to connect 6 External Connections to 1 machine.
I’ve heard a little bit about router and i know this can help me but is every router manageable/configureable? is there any way that i can solve this issue without a router?