I think brand of ram / voltage is your problem.
I've just built a p965ry and noticed a gigabit lan issue.
I was using Corsair 5-5-5-12 1.9v ram got a puase on power up but with no beeps.
I did have to disable lan in the bios even after updating bios thru a usb device and get a network...
I've just installed a g965RYxx (Has little IDE) that failed to load its drivers for the gigabit Lan.
I would say maybe try to go for the more expensive model P975s.
Go for the crossfire IMO
If anyone else has had problems with their Lan on a 965 please let me know how to relieve.