You have a motherboard with a dedicated CPU and RAM just for the network capabilities? Which brand and model is that?
My motherboard has dual Gigabit LAN too (of which I am using one) but it's not anywhere near the same technology as is offered by the Killer card.
It's a EVGA 680i. It has some integrated thingy called "first-packet technology" that prioritizes online gaming to lower pings. Prolly not as advanced as killer, but I'm out of PCI slots.