hi,i hv an xfx ati 4670 ddr5 1gb but i feel its not giving a decent enough performance with my new system-x2 555 3.2ghz,4gb...i would like 2 know which is a good replacement for this 1...(my psu is 450w only)...also i hv a budget of around 100-120 $....i like 2 play graphic heavy games