what gpu should i buy

Solution
GTX 760
http://www.misco.co.uk/product/199840/Asus-GeForce-GTX760-DC2OC-2GB-PCI-Express-Graphics-Card
Radeon 7950
http://www.misco.co.uk/product/193815/Sapphire-Radeon-HD7950-3GB-Over-Clocked-PCI-Express-Graphics-Card

Radeon 7970 (if you're considering paying over your budget)
http://www.misco.co.uk/product/193784/Asus-Radeon-HD7970-3GB-PCI-Express-Graphics-Card

Just check if your PSU has 8 and 6 pin (ideally 6+2 so you can mix and match) PCI-E power connectors since these cards require those (the 760 I linked needs 1 8 pin for example)
GTX 760
http://www.misco.co.uk/product/199840/Asus-GeForce-GTX760-DC2OC-2GB-PCI-Express-Graphics-Card
Radeon 7950
http://www.misco.co.uk/product/193815/Sapphire-Radeon-HD7950-3GB-Over-Clocked-PCI-Express-Graphics-Card

Radeon 7970 (if you're considering paying over your budget)
http://www.misco.co.uk/product/193784/Asus-Radeon-HD7970-3GB-PCI-Express-Graphics-Card

Just check if your PSU has 8 and 6 pin (ideally 6+2 so you can mix and match) PCI-E power connectors since these cards require those (the 760 I linked needs 1 8 pin for example)
 
Solution