Upgrade from a i3 3220 for a casual gaming

[nic8]

So far my i3 has been sufficient for gaming but since there are finally coming out some new titles like gta 5 where 4 core i5's provide something like +20-30% fps increase I am looking for a minor and cheap upgrade. Since I don't plan on upgrading my MB I am looking for used i5's. I am being offered SB i5-2400 (80 EUR) and a IB i5-3350P (135 EUR) or i5 2500K+MSI P67 MB for 150EUR. That i5 2400 price looks tempting but will it provide sufficient boost to my performance in multi core applications or should I go for much more expensive 3350P or even 2500K? My current mobo is H67 so no OC is possible and GPU is gtx660. That 2500k looks like a best offer but I am afraid that I will need to buy new PSU and a good heatsink If I want to OC it. And that's out of my planned budget.

 

[shivababbli]

without overclock also i5 2500k will give you a decent upgrade over i3, do not overclock for sometime and when you have some money , you go for 3rd party cooler and psu

 

[DeathRabit]

Yes I5 2500K is decent CPU