Pra5hant_P :
Vexillarius :
First thing I noticed is the PSU. I wouldn't run a £1000 build on a Corsair CX. Get an EVGA Supernova G2/P2 or a nice XFX or Antec instead. Anything Tier 1 or Tier 2 A or B with enough wattage/amps from here will do:
http://www.tomshardware.co.uk/forum/id-1804779/power-supply-unit-tier-list.html
To answer your question I'd need to what you're planning to do with the system. For gaming X99 is completely pointless, Haswell-E actually performs worse in games than the i7 and even an i5-4690K would be plenty. For editing/rendering/etc Haswell-R can be a good choice.
Hi there, I'll be using the build for 1080p (Maybe 4k) gaming, but will also use it for music production, Photoshop and maybe some video rendering. Also, can you recommend a decent PSU please?
In that case I'd get the Z97 build and seriously consider getting an i5-4690K. Incidental editing/etc doesn't justify X99, and it doesn't really justify an i7-4790K either.
As for the PSU, you can't go wrong with an EVGA SuperNOVA 850 G2. Good price, and you can SLI and overclock to your heart's content without worrying:
PCPartPicker part list /
Price breakdown by merchant
Power Supply: EVGA 850W 80+ Gold Certified Fully-Modular ATX Power Supply ($114.99 @ NCIX US)
Total: $114.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-10-20 11:28 EDT-0400
If you don't plan on overclocking/SLI'ing you can also get a 550w XFX:
PCPartPicker part list /
Price breakdown by merchant
Power Supply: XFX XTR 550W 80+ Gold Certified Fully-Modular ATX Power Supply ($74.99 @ Newegg)
Total: $74.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-10-20 11:29 EDT-0400
EDIT: 8GB RAM is plenty for what you'll be doing. The only things that'll use more than 8GB is, again, editing/rendering and if you don't do that a whole lot I can't really justify spending a bunch of money on extra RAM.