have a bugget of £50 pounds, which is the best graphics card to buy for the M5A78L-M/USB3 Motherboard?
This is about the best you can do for that amount of money. http://www.ebuyer.com/190139-sapphire-hd-5670-512mb-hypermemory-gddr5-hdmi-dvi-vga-pci-e-graphics-card-11168-06-20r
It will be fairly good at gaming if you game at 1680x1050 or lower. Some more demanding games will require you to back off on some of the eye candy.