The only other "significant" option would be to do a crossfire. And you will need a 750w psu.
PCPartPicker part list:
http://uk.pcpartpicker.com/p/O9z5
Price breakdown by merchant: http://uk.pcpartpicker.com/p/O9z5/by_merchant/
Benchmarks: http://uk.pcpartpicker.com/p/O9z5/benchmarks/
CPU: Intel Core i5-3570K 3.4GHz Quad-Core Processor (£167.99 @ Aria PC)
CPU Cooler: Cooler Master Hyper 212 Plus 76.8 CFM Sleeve Bearing CPU Cooler
Motherboard: ASRock Z77 Extreme4 ATX LGA1155 Motherboard (£103.46 @ Amazon UK)
Memory: Corsair Vengeance 8GB (2 x 4GB) DDR3-1600 Memory (£44.98 @ Amazon UK)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive (£50.00 @ Ebuyer)
Storage: Samsung 840 Series 120GB 2.5" Solid State Disk (£75.29 @ Amazon UK)
Video Card: Gigabyte Radeon HD 7970 3GB Video Card (2-Way CrossFire) (£309.98 @ Amazon UK)
Video Card: Gigabyte Radeon HD 7970 3GB Video Card (2-Way CrossFire) (£309.98 @ Amazon UK)
Case: Cooler Master Storm Enforcer ATX Mid Tower Case (£65.99 @ Aria PC)
Power Supply: Corsair Enthusiast 850W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply (£89.98 @ Dabs)
Optical Drive: Asus BC-12B1ST/BLK/B/AS Blu-Ray Reader, DVD/CD Writer (£45.29 @ CCL Computers)
Operating System: Microsoft Windows 7 Home Premium SP1 (OEM) (64-bit) (£68.35 @ CCL Computers)
Total: £1331.29
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-04-03 15:05 BST+0100)