It's fucking ridiculous how much more we pay for PC components than our Merkin' brethren.
Here's a fucking awesome build I stuck together in literally 5 minutes. It's got a haswell i5, 8gb RAM, a 7870 GPU and an SSD. For this price, it's simply pissing me off that we'd pay almost the same numbers, but in pounds.
http://pcpartpicker.com/p/2eY9b
You can leave out the SSD and go for a better GPU, but to be honest this one should be fine. I've also included 1tb of storage which should be enough for your video editing needs, and it;s a damn fast HDD too. An SSD will change the way you look at computing,
You could go for an AMD build and save about 50-100 bucks, but given you're not a hobbyist and this is to last you a while, just stick the best you can afford in there and be done with it.
This is also assuming that you have an OS, if you don't, let me know and we'll have to tweak it a bit.
ALTERNATIVELY:
http://pcpartpicker.com/p/2eYuh
This is an AMD build. The CPU has two more cores which will speed up your rendering a bit, and it's also got double the RAM at 16gb. It's also got a considerably more powerful graphics card which is excellent for gaming, and as far as the 760s go, this is the best, hands down. The trade-off? Slower per-core performance. You probably won't notice it, but it'll be there. The Intel will also last longer, although how much longer, I can't really say. This build also has a whopping motherboard with features that piss all over the Intel's, so if you want, you can always crank back on the motherboard and shove that cash elsewhere.
At the end of the day it's up to you. We've reached a point in CPU terms where things are stagnating for desktop gamers. The CPU manufacturers are aiming for lower power consumption and more mobility, which for the rest of us means that the performance is at a level which isn't going to be raised any time soon. Provided you're not looking at a $40 CPU, you're pretty much set, although the two listed here are pretty much the best at what they do, hands down.
As for graphics cards, there is so much competition going on between Nvidia and AMD at the moment that they've both had to slash their prices to remain competitive. A $500 card last year is now going for $300, a fact that PC gamers are more than happy to point out.
Let me know what you think.