I haven't seen any and dont know why you would need one PCI is fast enough for a NIC.
i had to go back to a pci 10/100 card which sucks cus i can tell the difference when i play games.
]Hey and if you are looking to do that but also want to ugrade your mobo you should just get a new mobo with a built in gigabit networkcard, somehow mine screwed up and i had to go back to a pci 10/100 card which sucks cus i can tell the difference when i play games. ANd the onboard was 4X faster which pisses me off, i need to fix that.