Overclocking i5 3570k on 4+1 phase (MSI z77ma-g45)

Do you guys think it'll be safe to push 4.5+ghz?

I wouldn't do it. The VRM components on that motherboard are pretty cheap and the heatsinks are quiet small. I wouldn't go over 4.3Ghz. But it depends on how well your CPU overclocks. 

Also overclocking settings in the BIOS will be limited because it is a pretty cheap motherboard.

Also overclocking will void the warranty on the Intel CPU. You should purchase Intel's overclocking protection plan to be on the safe side!

-Fishymamba Intel Response Team http://bit.ly/IntelRally

If you're gonna do it, check if no vrm or mosfets at the powerphases get overheated too much (keep max at 60°. see if you have a sensor somewhere at the Vcore (phase mosfets) )

Or in any case, see if your mobo gets a nice airflow, especially over those heatsinks at the cpu.

And finally, with 4+1 phase, keep a very close eye on the voltages. See that de Vdroop compensation doesnt deliver voltage spikes. I dont have experience with OC'ing (recent) intels, but I think its safe to say a stable voltage withing acceptable bounds would be welcome.