ati gpu temp & test

hey as u can see in the pic my hd 4670 ddr4 idles at ~40 and load about 55 probably cause the fan i put on it is better then the stock one, the way i try a overclock is playin heavy for about 20 min to check for polygon lines. but i want to benchmark it with a program to post the results... what ya recommend me? should i try higher clocks? where to stop? which program?