I want upgrade is my PSU good enough?

Here is are my PC Specs 

CPU; Intel(R) Pentium(R) CPU G840 @ 2.80GHz (2 CPUs), ~2.8GHz FCLGA1155 socket (only up to second gen I5's i think)

MotherBoard; Giga H61M-D2H-USB3

Ram 2 x 4GB 1333 mhz

PSU;500w 80+ cer cant find model number 

GPU; Sapphire 6870

I want o upgrade to the i5 2500k can my PSU handle this and is their any another processor i could go for 

A 500w PSU is plenty for most single GPU setups. You should be fine.

thanks mate 

psu's fine, but why put a unlocked processor onto a locked board? with a old gpu (unless otherwise stated I assume all machines are for gaming around here)

I would just go with an i3, unless you just got an amazing deal on the 2500k. If so, your PSU should be good to go. Also, I would drop $20 on an aftermarket  cooler. You should be able to get ta budget tower cooler for that price. It really makes a difference. If you can spare $30, go with a Cooler Master 212, under that you may need to do some research, but there are some great deals out there. For an i3 and lower, the stock cooler works great. Once you go i5 and up, it really is worth a few bucks to go aftermarket.

In a word? Yes.

I already have a after market cooler a real heavy one, i mean i'I've been doing my research and i feel its best for me to get a new mobo and just go the i5 3570k which will also allow me to over clock 

Make sure the motherboard has a Z77(for ivy bridge CPUs) or a z87(for haswell CPUs) chipset to ensure proper overclocking ability.

The i5-3570K is an Ivy Bridget CPU.

The i5-4670K is a Haswell CPU.  Haswell is the latest, but only has about a 5% increase in performance over Ivy bridge.