Charlatan

Yes, and the items you have linked to are from a US seller http://www.ebay.co.uk/itm/Gamer-PC-Intel-Core-I7-6700K-16GB-RAM-3GB-Geforce-GTX1060-1TB-WIN10-PRO-WLAN-/401181796421?hash=item5d684c6845:g:2IgAAOSwaB5Xvu4d would be about the best you will find with a 6700k. However this will not overclock due to the motherboard

It would, with the graphic card, however, it would cost a fortune in shipping and customs charges from the USA

The machine you linked to on ebay has a 4790 cpu, NOT a 4790k, and only has onboard graphics, not a dedicated video card. In short - junk You'd be better off buying this, http://www.ebay.co.uk/itm/FAST-GAMING-EDITING-PC-LIQUID-COOLED-OVERCLOCKED-CHEAP-/201659441599?hash=item2ef3d6e1bf:g:oUEAAOSwFe5XybM2 then buying a GTX970 or 1060 to plug into it

Unfortunately, that is junk. Are you able to build yourself?

Ouch

Not too sure about @ 1600*900, but there isn't a machine in the world that will run what you want @40fps at 1080p, I would highly doubt that a 970 would get anywhere near that. If you back the sliders and anti aliasing etc off a bit, you may get 30fps with a 970. Could you stretch to a 980Ti now that they have come down a hell of a lot?

1 - 1 and no 2 - no 3 - probably not 4 - 8gb is enough My advice? Hang fire a bit longer and save a bit more. You want a better video card, and better cooling. The 6600k isn't an issue as opposed to the 6700k, but would recommend a 1060 at least (pref a 1070) and either a Noctua 15 cooler or a Corsair H80 or better for cooling

Solid choice

GTX 1070, slightly faster than the 980Ti, 2gb more memory, and will only get faster as drivers improve

I paid £13 for a kosher Windows 10 the other week. You can get Win 7 for similar too

Change the RAM for 3200mhz stuff

Fly forever is spot on. Send the 1080 back, and get a 1070 or 1060 and a 6600k and motherboard

Definitely sounds like a PSU or shorting related problem. If you get no joy, try taking the mpu out the case, and put it on say the motherboard box and try that. I had a short from the case one time that caused the same issue

Only advantage would be faster loading. If you are working to a budget, ignore the SSD (certainly over compromising on any of the other core components) and stick to HDD. You could always add an SSD on at a later date.

Ah, in that case 99.9% you would need to change the motherboard as well. These proprietry motherboards usually have no overclocking options