Notes from Today’s Slash discussions and my own research.
SMC8508T 8 port gigabit switch. Supports jumbo frames and costs $150.
Intel Pro 1000 cards seem to get a lot of good reviews. Jumbo frames and linux support. 66mhz, but only 32bit. But cheap at $35 or so.
Your slow PCI bus will hurt you. Intel makes a MLB with built in Gig-e that has a dedicated channel for LAN. Intel 875P and Asus P4C800E Deluxe seem to be good intel choices. Nforce 3 boards have something a lot like this. If nothing else get 66mhz PCI slots.