What graphics card should I get for my computer?

[Bailout1]

I've got around £80 to spend on new graphics card as my old one (Radeon 5450) needs updating.

Computer Specs:
CPU: AMD Phenom(tm) II X4 830 Processor (2.80Hz)
Graphics Card: AMD Radeon 5450
Ram: 6GB
Memory: 1TB

 

[Bailout1]

not too sure how all the UK pricing is right now

It's about $125