I think that you have your finger on some of the problem. The XP TCPIP stack handling is not suited for multiple small packets in gaming.
I just made the jump to an M1 Killer NIC and performance rocketed. Its a fully embedded Linux computer on a NIC and takes the stack handling, MD5 checks etc off the CPU similar to an X-Fi sound card taking DSP away from the CPU. Pings dropped 20ms, frame rate went up 15fps, CPU load dropped 10-15%.
If the card had a hole............... |