if you plan on editing 4k media and exporting 4k the 6 core i7 will be a better option. however, even with the cheapest of gear like the i7-5820k and cheaper motherboard etc, the build will be over your budget unless you can carry over some gear from an existing pc.
if your budget is that tight and you can wait a while, you may want to wait to see how amd's ryzen performs and/or if intel drops prices to compete. ryzen should be the best value for performance, but its unknown if there will be any compatibility bug issues with ryzen and adobe software.
Definitely x99! Go for the affordable 5820k or 6800k for now, and then if you ever need even more CPU "power" you only need upgrade your CPU.
Definitely too go for a NVidia GTX video card. Adobe Premiere Pro does timeline editing so much smoother with one when you're editing 4k.
I agree with both Ronin and Jim. In addition, you do not want to buy a seriously imbalanced configuration by going big on the CPU (such as the i7-6800K) but severely underpowered on the GPU (such as anything below a GeForce GTX 1050 Ti). So, in your price range a combination of an i7-6700K and a GTX 1060 is way better than a combination of an i7-6800K and only a GT 730. But if you want your new system to comfortably handle 4k video editing, I'd strongly recommend increasing your budget to well above £1500.
Thanks guys. I'll hold out for a few months then.
Ok so I've come to terms with the fact i probably can't afford a 6core any time soon, sadly, so it makes me think whether to go the cheaper route, and then look to upgrade again in say 5 years time.
How does this look? A barebones unit without OS, Hardrives or Optical drive, but i can recycle my Optical drive, get Win10 for £25 on softwaregeeks, 128gb SSD for the OS for £50, and 2tb 7200rpm HDD for £80ish.
£685 + £25 + £50 + £80 = approx £815
Then I'll keep an eye out for GTX deals.
What do you guys think?
That's a massive help! Thanks mate. I'm really surprised with the results. 5-15% performance differences with the 6core 6850 and 10core 6950X. Definately expected more! Mostly noticeable at 4k too, which is a few years away for me as I'm still happy with 1080p/60 for the timebeing.