Is this 550W PSU good enough for overclocking?

[Manderville]

Is my Supernova G2 550W PSU enough for overclocking my CPU and maybe my GPU or do I need more ?

My build: http://pcpartpicker.com/p/wGCbbv

 

[Hawkshot]

Yes you should be fine but you are pushing fairly close to the Max load of that PSU even though its amazing quality it will be able to do it but wont give you much headroom

I have a very similar build to you with an OC i5-6600k and an R9 290X but I use the 650w G2 PSU for the reason as I knew I would be pushing the power limits

 

[BadActor]

I calculated your usage at 469 watts, so the PSU should handle it, but I agree with the above, a 650 or larger would be a better choice.