I'm guessing but you are not the network administrator right? If I were you I check out ganging NIC's. Linux has no limit to the number of ganged NIC's (of course the hardware does). From Adaptec you can buy NIC's with four ports and most boxes will support two cards - 8 ports total. If that does not work I would really check out some of the high end network setups. I have never used any but I've read about them. TByte transfers per second. Of course that is if money is not a problem.

Of course you can also segment the network. Provide a DBF file server on a different segment. Add a second NIC to the workstations to allow access to the different segments of the network. I have done this in the past to allow a workstation access to different segments of a WAN and LAN.

After that I'd call for some help from the big ISP type guys. Some how they are able to support millions of connections and tBytes of transfers without to much trouble.
Johnf