don't base your selection due to the fact that it has a genuine copy of windows 7.. that is the last thing you should be thinking about when pc hunting (well, building one at least)
i've built a similar PC (with an OS as you seem to want) on pcparts to see if you would be saving much, and you do just a bit
PCPartPicker part list:
Intel Core i7-4790K, Corsair 200R - System Build - PCPartPicker United Kingdom
Price breakdown by merchant:
Intel Core i7-4790K, Corsair 200R - System Build - Price Breakdown By Merchant - PCPartPicker United Kingdom
CPU: Intel Core i7-4790K 4.0GHz Quad-Core Processor (?259.99 @ Aria PC)
Memory: Corsair Vengeance Pro 16GB (2 x 8GB) DDR3-1866 Memory (?87.03 @ Ebuyer)
Case: Corsair 200R ATX Mid Tower Case (?49.19 @ Aria PC)
Operating System: Microsoft Windows 7 Home Premium SP1 OEM (64-bit) (?67.95 @ Ebuyer)
Total: ?464.16
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-07-05 22:46 BST+0100
~15 pounds difference. is that a deal breaker? absolutely not. you're better off choosing your own parts if you ask me. however, you do choose to go with that, know that you need to have a LGA1150 motherboard and a GPU..
you should be investing more time into the essential parts, not peripherals or windows. that should be the last thing you think about.