I am on a budget and i can overclock core i3 on stock heatsink but not core i5 also i can spend money left from buying core i5 750 for better gpu.
I will upgrade system after 2 years.
Do you want 4 full cores or 2 cores with 4 threads? Core i5 6xx processors I think are too expensive. Get the Core i3 540 and put the rest of your money into the motherboard and Graphics card.