yes, the i3 2120 WILL perform SLIGHTLY better but it is a HUGE waste of cash. I would wait for haswell/piledriver ATLEAST. However if you NEED to upgrade now (i dont see why your system looks fine albeit with a below average cpu) ATLEAST get an i5 3570 (non k since you arent going to overclock)
I'm also waiting for the pile driver
the reason i'm buying a rig is because I'm selling my old one. hmmm makes me think though...
I'll just stick with my laptop till the pile driver will be out