You can spend extra to get i7, but in order to get better performance on games, you will be better saving the money from i7 to i5, and spend it on video card
If you go for i7, i7 4790 is what you need.
If it is i5, i5 4690.
Have you already get 6670? why going for 6670? That is outdated.
PSU - go for brand like Seasonic, Antec, Corsair, XFX
Be quiet! if you are in Europe
if you want something good value for money, look for Corsair CX500 or EVGA 500W