The 7660D is close to the settings of the HD 6570 and Diablo 3 isn't all that demanding and so far you spec's cover it. The mim of a card for the best game play is a 4870 and up.
Your card is under that but not to far down. The mim GPU required is a X1950 which puts your card in the middle of the two. Bottom line not high settings but med for sure. Here is the CPU chart. Good luck to you.