Intel core2 duo vs i3 upgrade need help

Hello,
I am trying to play swtor, which is pretty CPU heavy.
ATM Im being bottleneck by my processor(I think) which is a pentium D 2.8 mghz(2 of these). While my you is the ATI RADEON hd 4790 1024 mb,which is far superior to the CPU and for someone that doesn't care about about quality of graphics but wants a smooth fps game play it's enough.
So I have the
Option of getting a core2 due( don't know which but I was told that was superior to the i3 one in speed.)....or an i3.
My budget is small and limited and the mobo and ram for the i3 kinda make me go over it.
And with the core2 duo I could still use my ddr2 ram and only buy the
Mobo for it.

So would a top core2duo surpass my pentium d enough for me to actualy play swtor above 20 fps?having a small budget and all.