If you can post the hardware ID and driver version of the NIC's you've tried, we can look into it.
I'd be happy to. Is there a way to find the hardware ID and driver version of the NIC's without reinstalling each one again? Perhaps it's in a log file somewhere? I think I tried about 6 nics before the current Realtek RTL819/810x (which is still showing very low DPC latency after a couple of hours of running - very promising!!!)
Darryl Gittins