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The interesting thing is that your CPU is a tenth of the cost of one of my CPUs, and yet in terms of performance it's not far from what one of mine delivers.
The only real differences emerge in the bandwidth available to each CPU from RAM, and the ECC RAM support. But unless you're doing some incredible throughput and maxing it out, it's not going to make a difference. For the vast majority of workloads, because 3D rendering and even Photoshop would outsource some work to the GPU... you're actually going to see performance on par with my insane system.
This is why... when I finally do need to replace my machine, I'm unlikely to go back to a workstation class machine. I love my machine, but outside of the first 6 months of running a lot of VMs concurrently, it's just overkill and doesn't represent bang-for-buck.
Mostly games and 3D modelling/rendeirng plus a bit of photoshop.
The 6700k is probably overkill for games at the moment, since even with dual 780s I'm usually GPU limited at 7560x1440. Having said that the upgrade from Sandybridge to Skylake does apparently improve SLI performance, particularly in terms of minimum frame rates or 'stutter'. Am also hoping that since the 2600k lasted over five years it'll be about as future-proof as technology gets.
For the 3D stuff, rendering would definitely benefit from more than four cores (or more than one CPU) but practically everything else is still single threaded so overall clock speed is more beneficial. The likes of Xeons and Quadros are so expensive compared to the regular consumer stuff they've never appealed for my uses.