I've tried to aim between your 2 example price points with a few nice additions, an SSD is absolutely essential IMO:
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor (£167.94 @ Scan.co.uk)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler (£24.25 @ Scan.co.uk)
Motherboard: Gigabyte GA-Z97M-D3H Micro ATX LGA1150 Motherboard (£79.16 @ Scan.co.uk)
Memory: Kingston Fury Series 16GB (2 x 8GB) DDR3-1866 Memory (£114.24 @ CCL Computers)
Storage: Crucial MX100 256GB 2.5" Solid State Drive (£77.10 @ Scan.co.uk)
Storage: Seagate Barracuda 2TB 3.5" 7200RPM Internal Hard Drive (£60.04 @ Amazon UK)
Video Card: Sapphire Radeon R9 290 4GB Tri-X Video Card (£295.55 @ Scan.co.uk)
Power Supply: EVGA 600B 600W 80+ Bronze Certified ATX Power Supply (£43.32 @ Amazon UK)
Other: CoolerMaster Silencio 352 Black Matt Edition USB3 MicroATX Mini-ITX Case (£45.63)
Other: Powerline Adapters - 2x 200mb with AC passthrough (£22.98)
Total: £930.21
The powerline adapter listed is far preferable to wireless if you've got a single power circuit shared between your router and PC. There's also a
non-passthrough version (£19.30) and a
non-passthrough 500Mbps version (£24.99)
The 4690k is preferable to the 4670k for an extra couple of quid, the memory is cheaper and faster (not that this makes a huge difference depending on who you ask).
I've also changed the PSU to one of my favourite 600w units to save money without cutting down on quality - it's worth mentioning that this isn't modular though so it depends how happy you are about cable management in your chosen case - I have no experience with it.
The GPU is a step up from the 280x and provides GTX 780 levels of performance for a very reasonable price.
This is all completely flexible for your tastes and needs of course, I also thought I'd mention the
Fractal Define Mini as an alternative silent mATX case, this will run you around £61.99.
Any questions please ask!