Used I5 3340 Vs Fx 6300 Plz Help.

Hi, I am in dilemma plz solve my issue. Actually I am having Intel Pentium G2020+h61m MB. It is giving bottleneck to my GTX 660 2GB while playing GTA 5 (even at low - medium settings at 1080p). I am getting second hand i5 3340 for Rs. 6.5k (without any bill, box and fan) and FX-6300+GA-78LMT MB for Rs. 7k (without box but with bill having 2 years of warranty). So what should I prefer.

PS: I am not gonna upgrading my PC for next 2-3 years as I am student who do not earn anything.