I like X99 systems.
They are awesome, but overpriced.
If I was on the market for NEW rig with 5000$ budged, I would choose X99 and X5960.
For the money you get true versatile performance rig which such good for games as for work also.
Moreover. You have upgrade gap for 1 CPU gen minimum, unlike Z99 it's a dead-end.
Anyway, there is an option for X99 rig - to go for a 5820k and upgrade in a 2 years for X5960, or next gen-8cores-CPU.
Although, I doubt that next 2-3 years games will "eat more that 8 cores".
Next-gen consoles just will not allow this.
So, X5960 - it's a best choice for games for the next 5 years.
16 threads are very cool in video and 3D editing .
P.s.
Personally, I see no reason for upgrade next 2 years with my system. I've read and watched tons of reviews and videos and see no sense for upgrade. The only thing that I'd like to have is real time full HD render on X5960 but when I count how much it cost... no no no. )))