Thanks a lot for the answers! Unfortunately, I'm even more confused now haha.
I don't plan doing crossfire in the future so if the 520W PSU is enough for my build I will get that one.
As for the mobo choice, what is the advantage of going Z68? I will use this computer only for gaming so I don't know. About the P67 boards I have also heard great things of the ASRock board but the Gygabyte one doesn't look bad either. Wich one do you think is better? ASRock P67 PRO3
or Gygabyte GA-P67A