PCPartPicker part list:
http://uk.pcpartpicker.com/p/tVCGxr
Price breakdown by merchant: http://uk.pcpartpicker.com/p/tVCGxr/by_merchant/
Benchmarks: http://uk.pcpartpicker.com/p/tVCGxr/benchmarks/
CPU: Intel Core i5-4690 3.5GHz Quad-Core Processor (£152.99 @ Aria PC)
CPU Cooler: Noctua NH-D14 65.0 CFM CPU Cooler (£57.89 @ Ebuyer)
Thermal Compound: Noctua NT-H1 3.5g Thermal Paste (£6.95 @ Amazon UK)
Motherboard: Gigabyte GA-Z87-D3HP ATX LGA1150 Motherboard (£76.64 @ Scan.co.uk)
Memory: Corsair Vengeance 8GB (2 x 4GB) DDR3-1600 Memory (£55.34 @ Scan.co.uk)
Storage: Samsung 840 EVO 120GB 2.5" Solid State Drive (£54.99 @ Amazon UK)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive (£35.94 @ Aria PC)
Video Card: Sapphire Radeon R9 270X 2GB Dual-X Video Card (£129.00 @ Amazon UK)
Case: NZXT Phantom 410 (Black/Orange) ATX Mid Tower Case (£79.69 @ Scan.co.uk)
Power Supply: Corsair CX 600W 80+ Bronze Certified Semi-Modular ATX Power Supply (£52.27 @ Amazon UK)
Optical Drive: Samsung SH-224DB/BEBE DVD/CD Writer (£10.84 @ Dabs)
Operating System: Microsoft Windows 7 Professional SP1 (OEM) (64-bit) (£59.00 @ Amazon UK)
Wireless Network Adapter: TRENDnet TEW-805UB 802.11a/b/g/n/ac USB 3.0 Wi-Fi Adapter (£21.98 @ Amazon UK)
Total: £793.52
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-05-31 17:55 BST+0100)
This is what I would recommend. I have changed: case (this one comes in a multiude of colours http://www.nzxt.com/product/detail/95-phantom-410-mid-tower-case), RAM/memory, CPU, CPU cooler, motherboard. I also added in some better aftermarket thermal paste which will come handy and help keep your CPU cooler than stock.
My reasonings for changing:
Changed the Zalman Z11 plus case as although it is cheap and looks good the fan are terrible and it is hard to get to top/front for fan cleaning/removal; I have this case myself.
Changed RAM as Corsair is one of the best, if not the best RAM manufacturer out there.
Changed CPU as intel is generally better for gaming and you are not likely to need 8 cores unless you intend to be running servers or VMs etc.
Changed CPU cooler as Noctua are some of the best coolers.
Changed motherboard to be compatible and is a decent board with features for its price. You may wish to change to an Asus motherboard but that is up to you.
Thanks for reading,
Nxl8