I currently use EVGA Precision X for GPU overclocking because I have an EVGA GPU, but I have used MSI Afterburner in the past. They both work well for me, so I have no preference.
For CPU overclocking, I only use the BIOS.
I use HWinfo64 for monitoring system speeds, voltages, and temps, plus CPU-Z and GPU-Z for extra details on those specific components.
And the only way to know if you can overclock is to go ahead and try to overclock. You should be able to find out quickly whether it'll work or not. You likely won't actually damage anything, it just won't be stable if the power supply isn't giving good power.
I would definitely recommend staying below 4.2GHz or so with that power supply, even if it is successful. You don't want to be pushing it too hard.
If you really want to overclock, I'd recommend saving up about $80 or so and getting one of these three:
EVGA SuperNOVA G2 550W
SeaSonic SSR-550RM 550W
XFX TS 550W
They all have enough power for pretty much any single CPU, single GPU setup that's fully overclocked.