Here's a brief introduction to the Intel i3 processor evolution -http://en.m.wikipedia.org/wiki/List_of_Intel_Core_i3_microprocessors
In a nutshell, all i3 processors, irrespective of the generation, are dual cores. For your intended purposes, i would recommend getting a proper quad core ( i5 ) though. Something like an i5 3450 should serve your needs well enough. That's of course depending on how much are you willing to pay.