Unlocking Cores

Hey guys I'm good at Pc's but not very good at overclocking or unlocking cores.

Here's my setup

AMD X2 560 3.3Ghz

MSI 785GM-P45

2gb Crucial DDR3 Memory

On the processor I see on newegg that everyone has unlocked the 2 extra cores, and overclocked it alittle bit to about 3.5 - 3.9 Ghz which is pretty cool.

With the motherboard I managed to get the 4 cores with the core unlock option in the Bios and then it rated -2 per core, left it that way since I did'nt know what the hell that was maybe the voltage.

I'm a little bit worried about the ram but times are tough so I'll manage to get some more soon.

My main concern is the people who purchased the processor recommended a better heatsink, and also what does the voltage (-2,-4 etc) thing mean if i raise it will it increase the speed but increase the heat meaning that it will need a better heatsink.

So far I left the stock fan heatsink on it and two (80mm) fans one on the front and one on the back.