Kopil Goyary

Q4. fx-4300 and 1080. Best build you can do.
Seriosuly tough, 1060 coming today/tomorrow so you can wait for that or go with 6500/6600 with z170 or h170 chip mobo and 1070. Dont get unlocked cpu's if you dont get z170 with it.

If buying an i5 then 1060
If buying an i7 then 1070/1080

I5s bottleneck higher end GPUs

Most people are i5 fanboys. Here is a video thread
 

Not a i5 fanboy, but im not big fan overpriced cpu's that give you little bit of extra fps in games. My i5 is holding 980ti just fine in 1080p, but i onyl have 60hz monitor so theres that also. Not everyone has higher end monitors

That Xeon doesn't run on consumer boards I believe - it requires a different socket.

Also - games are leveraging multiple cores - 4 is now the bare minimum and you can see a notable difference of 20%+ in quite a few games when testing i5s vs i7s

Nowadays 1080P huh More like 720P  .
Anyways, Both RX480 and GTX1060 are capable of playing most modern games at a constant 60+fps on high/ultra settings at 1080P so you don't have to worry about 1080P gaming. It all comes down to the price of the gpus at your location and personal preference.

Thks I'll look into that, I very much appreciate your suggestion  

The problem with this PSU is that the CPU power connector is too short, at the minute im having to run it under my cooler and it only just reaches ahah. I'm also going to be selling my old rig to a friend, minus the SSD and CPU cooler of course.

The PSU is mediocre, Get an EVGA G2, B2, GS, GQ, P2, Anything from Seasonic or XFX (excluding the XT), the Corsair RMi, RMx, HXi, AXi. 
A Z170 motherboard will not effect performance is not needed since the CPU is locked and cannot be overclocked. I'd get a H170 or B150 motherboard instead since they are often a lot cheaper.
DO NOT do a dual GPU settup, they just make your life harder. Something like a RX 480, GTX 1060 and previous generation cards on clearance are also good choices.
(GTX 960 < R9 380 < R9 380x < GTX 970 = RX 480 < R9 390 < R9 390x < GTX 980 < R9 Nano < Fury < Fury X)
 
An SSD is recomended, the Kingston SSDNOW UV400, Samsung 850EVO and ADATA SP550 are very good budget SSDs.

Okay.
Your system will run perfectly even with 700W(850W on your part list is way much).
And i5-6600K is good but having i7 makes it easy for you to get a better gpu in future.(If you are not planning on changing your gpu for next 1-2 years, getting an i5 will save you a lot and you can get a M.2 storage).
 
If you are planning to use your system for streaming and video editing, get i7. 
I guess there is no point in getting i5 if you already have the budget for i7.