Ok, This thread has gotten insane, people haven't read half of it,and giving advice.
The 980x is a great choice for your son. He will use it. The Rampage III you added is great also. I have both, and can't complain. Any of the high end 1366 motherboard are good quality though. Keep that in your cart, you can't go wrong, for RAM, I would suggest
The only problem with that memory is that it will use up all the slots, if he wants to go to 24GB, he'll have to replace all of them, but 12 should be enough. Maybe someone that does more video editing stuff will be able to correct me there.
Send me a PM if you want, and if you have skype, that works better also, as you can chat in real time. But there is a lot of different opinions on here, and I think a lot of it has to do with not reading the thread through. (some still think you have $4K left to spend).