just buy an Intel workstation or server card if you're will to spend the money on a "gaming" NIC.
There does seem to be somewhat of a diff with NICs.
My brother has an integrated RealTek NIC and a full namebrand custom built computer with an i7 2.66 OC'd to 3.9 and I have a crappy store bought Dell with an integrated Intel NIC.
When he comes over to play at my house, I get 80-90ms in game pings with BC2, but he gets 110-120ms.
I have no MAC/computer specific QOS, so it's not that and We both have Win7 with default Installs, no reg tweaking/etc.