I don't believe a router is what you want to use here, you'd be better off having a simple hub or switch and simply use Internet Connection Sharing (I'm assuming your running a version of Windows on the machine). Have your machine be the "router" for the other systems in other words.
Even better would be to install a wireless router/switch and let it do all the work. There are quite a few good ones on the market. Then the other systems wouldn't be dependant on the one with the 350 PCI card being on for gaining access to the internet and/or printer...