The 980x will be out this as Psycho said or the next week.
At Tom's there was an review. There are already gains in some apps from 6 cores
And i said 12gb because if you're building an rig with that king of CPU's, you probably are going to keep it for at least 3-4 years;), right? Not that 6GB is bad, no it's not bad at all, it's just above mainstream-high segment.
But as i said 12GB paired with Core i7 980x is going to give you a more powerful system for the years to come