Do you have money to spend on a better monitor? Using an 8320 and a 7950 on a 1366x768 monitor is a tad of a waste. Especially because it's the devil's resolution.
If you would, a 7870 GHz edition or an R9 270X with a larger, grander monitor might be a better tradeoff, especially because you won't need to use anti-aliasing to eliminate jaggies at 1920x1080 and would thus tax your hardware less.
At this price point, the 83xx AMD chips are really nice. No point trying to get an Intel build with a quad-core, in my opinion. I do use Intel. Put simply, Intel is more expensive than it is worth.
You could go with a much cheaper FM2 or FM2+ platform(s), in the interest of saving money. However, it wouldn't be as powerful.
For £600, the 8320 and 7950 is all pretty high-end stuff.
Yes and no. You could get real lucky with the 8320, and have it overclock all the way up to an 8350, and then some.
I think the 8350 is better for productivity, where you want to squeeze every bit of performance out of the chip. If you're gaming, the 8320 is just as good.
You'll have the 8 cores that games like Battlefield 4 are starting to utilise. They are the same chip, but the 8320 is clocked lower.