Can i overclock this CPU

You cannot overclock with factory cooling. I mean, you can try, but you'll just do damage. How much damage, that varies. The CPU approaches it's temperature limits just on stock settings, let alone overclocking.

43*C Idle? Run prime95 small fft for 15 minutes and tell me what your max core temp was.

As for power supply, wattage means nothing. You should tell us the exact model. Even if you have enough amperage on the 12v rail, what is really important is the voltage regulator on the PSU and if it can handle the high load variance that overclocking introduces. Which mediocre PSUs cannot handle.

Now that you already bought whatever PSU, I'd just try overclocking on it (unless it was a really bad psu or oem psu, as you can risk blowing out your entire system, which is a very likely scenario, not a risk but likely, on low quality psu's, oem psus, as they don't have overcurrent protections and proper traces).

But you'll pull your hair out when instability occurs because you won't know what component is causing the instability. You really should try an OCCT psu test to check your PSU's snuff before overclocking, if you want to continue with your psu though. I'm not going to say don't ever overclock on a psu that isn't high quality, but realize you are risking blowing out your entire system if the quality of the PSU is really bad.

Like if it's a corsair CX series, or thermaltake TR2, or OCZ modstream, meh, whatever. If it's some OEM or rosewill capstone...

I would say buy a different PSU before overclocking. Phenoms are quite power hungry. You will also need a better cooler. That psu is really bad, no overcurrent protections so the voltage regulator will blow out on a high load transcient.

Do you have a graphics card?

Why don't you just post exactly what specs and parts you have. That way we dont have to play a million questions.

Why would you plan to get a 7870? What games do you play, plan to play? I don't see that being a really good idea.

Wait until you get a new PSU to overclock. Phenoms can put out a lot of heat, so watch the temps very carefully, especially if you are using the stock cooler.