Best graph card for under £70

Hi guys i am looking for a new graphics card for my pc, i have completly custom built it in a small micro atx case which i built out of acrylic it has an amd x6 1055t cpu and 4gb ddr3 ram and a gigabyte udh2 motherboard and 2 seagate drives in raid array.i am looking for a graphics card for my system it can not be physically big not much bigger than a geforce 8500 in physical size however it can be slighly longer around 1 inch. i have heard the 4850 is an awesome card and it should fit in my case i can get one quite cheap but does anyone have any better ones they know about maybe something with dx11 it is going on to a 32 inch screen but at res of 1024*728. cheers adam